Pyrrolobenzodiazepine-antibody conjugates

ABSTRACT

A conjugate of formula (T): Ab-(DL) p  wherein: Ah is an antibody that hinds to AXL; DL is formula (A).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of GB1702029.8 and GB1702031.4, filed 8 Feburary 2017 and GB1719906.8 filed 30 Nov. 2017.

FIELD OF THE INVENTION

The present invention relates to pyrrolobenzodiazepines (PBDs) having a labile protecting group in the form of a linker to an antibody.

BACKGROUND TO THE INVENTION Pyrrolobenzodiazepines

Some pyrrolobenzodiazepines (PBDs) have the ability to recognise and bond to specific sequences of DNA; the preferred sequence is PuGPu. The first PBD antitumour antibiotic, anthramycin, was discovered in 1965 (Leimgruber, et al., J. Am. Chem. Soc., 87, 5793-5795 (1965); Leimgruber, et al., J. Am. Chem. Soc., 87, 5791-5793 (1965)). Since then, a number of naturally occurring PBDs have been reported, and over 10 synthetic routes have been developed to a variety of analogues (Thurston, et al., Chem. Rev. 1994, 433-465 (1994); Antonow, D. and Thurston, D. E., Chem. Rev. 2011 111 (4), 2815-2864). Family members include abbeymycin (Hochlowski, et al., J. Antibiotics, 40, 145-148 (1987)), chicamycin (Konishi, et al., J. Antibiotics, 37, 200-206 (1984)), DC-81 (Japanese Patent 58-180 487; Thurston, et al., Chem. Brit., 26, 767-772 (1990); Bose, et al., Tetrahedron, 48, 751-758 (1992)), mazethramycin (Kuminoto, et al., J. Antibiotics, 33, 665-667 (1980)), neothramycins A and B (Takeuchi, et al., J. Antibiotics, 29, 93-96 (1976)), porothramycin (Tsunakawa, et al., J. Antibiotics, 41, 1366-1373 (1988)), prothracarcin (Shimizu, et al, J. Antibiotics, 29, 2492-2503 (1982); Langley and Thurston, J. Org. Chem., 52, 91-97 (1987)), sibanomicin (DC-102)(Hara, et al., J. Antibiotics, 41, 702-704 (1988); Itoh, et al., J. Antibiotics, 41, 1281-1284 (1988)), sibiromycin (Leber, et al., J. Am. Chem. Soc., 110, 2992-2993 (1988)) and tomamycin (Arima, et al., J. Antibiotics, 25, 437-444 (1972)). PBDs are of the general structure:

They differ in the number, type and position of substituents, in both their aromatic A rings and pyrrolo C rings, and in the degree of saturation of the C ring. In the B-ring there is either an imine (N═C), a carbinolamine(NH—CH(OH)), or a carbinolamine methyl ether (NH—CH(OMe)) at the N10-C11 position which is the electrophilic centre responsible for alkylating DNA. All of the known natural products have an (S)-configuration at the chiral C11a position which provides them with a right-handed twist when viewed from the C ring towards the A ring. This gives them the appropriate three-dimensional shape for isohelicity with the minor groove of B-form DNA, leading to a snug fit at the binding site (Kohn, In Antibiotics III. Springer-Verlag, New York, pp. 3-11 (1975); Hurley and Needham-VanDevanter, Acc. Chem. Res., 19, 230-237 (1986)). Their ability to form an adduct in the minor groove, enables them to interfere with DNA processing, hence their use as antitumour agents.

One pyrrolobenzodiazepine compound is described by Gregson et al. (Chem. Commun. 1999, 797-798) as compound 1, and by Gregson et al. (J. Med. Chem. 2001, 44, 1161-1174) as compound 4a. This compound, also known as SG2000, is shown below:

WO 2007/085930 describes the preparation of dimer PBD compounds having linker groups for connection to a cell binding agent, such as an antibody. The linker is present in the bridge linking the monomer PBD units of the dimer.

Dimer PBD compounds having linker groups for connection to a cell binding agent, such as an antibody, have been described in WO 2011/130613 and WO 2011/130616. The linker in these compounds is attached to the PBD core via the C2 position, and are generally cleaved by action of an enzyme on the linker group. In WO 2011/130598, the linker in these compounds is attached to one of the available N10 positions on the PBD core, and are generally cleaved by action of an enzyme on the linker group.

Antibody-Drug Conjugates

Antibody therapy has been established for the targeted treatment of patients with cancer, immunological and angiogenic disorders (Carter, P. (2006) Nature Reviews Immunology 6:343-357). The use of antibody-drug conjugates (ADC), i.e. immunoconjugates, for the local delivery of cytotoxic or cytostatic agents, i.e. drugs to kill or inhibit tumor cells in the treatment of cancer, targets delivery of the drug moiety to tumors, and intracellular accumulation therein, whereas systemic administration of these unconjugated drug agents may result in unacceptable levels of toxicity to normal cells (Xie et al (2006) Expert. Opin. Biol. Ther. 6(3):281-291; Kovtun et al (2006) Cancer Res. 66(6):3214-3121; Law et al (2006) Cancer Res. 66(4):2328-2337; Wu et al (2005) Nature Biotech. 23(9):1137-1145; Lambert J. (2005) Current Opin. in Pharmacol. 5:543-549; Hamann P. (2005) Expert Opin. Ther. Patents 15(9):1087-1103; Payne, G. (2003) Cancer Cell 3:207-212; Trail et al (2003) Cancer Immunol. Immunother. 52:328-337; Syrigos and Epenetos (1999) Anticancer Research 19:605-614).

Maximal efficacy with minimal toxicity is sought thereby. Efforts to design and refine ADC have focused on the selectivity of monoclonal antibodies (mAbs) as well as drug mechanism of action, drug-linking, drug/antibody ratio (loading), and drug-releasing properties (Junutula, et al., 2008b Nature Biotech., 26(8):925-932; Dornan et al (2009) Blood 114(13):2721-2729; U.S. Pat. Nos. 7,521,541; 7,723,485; WO2009/052249; McDonagh (2006) Protein Eng. Design & Sel. 19(7): 299-307; Doronina et al (2006) Bioconj. Chem. 17:114-124; Erickson et al (2006) Cancer Res. 66(8):1-8; Sanderson et al (2005) Clin. Cancer Res. 11:843-852; Jeffrey et al (2005) J. Med. Chem. 48:1344-1358; Hamblett et al (2004) Clin. Cancer Res. 10:7063-7070). Drug moieties may impart their cytotoxic and cytostatic effects by mechanisms including tubulin binding, DNA binding, proteasome and/or topoisomerase inhibition. Some cytotoxic drugs tend to be inactive or less active when conjugated to large antibodies or protein receptor ligands.

The present inventors have developed particular PBD dimer antibody conjugates.

SUMMARY OF THE INVENTION

A first aspect of the present invention provides a conjugate of formula (I):

Ab-(DL)_(p)  (I)

wherein: Ab is an antibody that binds to AXL;

DL is

wherein: X is selected from the group comprising: a single bond, —CH₂— and —C₂H₄—; n is from 1 to 8; m is 0 or 1; R⁷ is either methyl or phenyl; when there is a double bond between C2 and C3, R² is selected the group consisting of: (ia) C₅₋₁₀ aryl group, optionally substituted by one or more substituents selected from the group comprising: halo, nitro, cyano, ether, carboxy, ester, C₁₋₇ alkyl, C₃₋₇ heterocyclyl and bis-oxy-C₁₋₃ alkylene; (ib) C₁₋₅ saturated aliphatic alkyl; (ic) C₃₋₆ saturated cycloalkyl; (id)

wherein each of R²¹, R²² and R²³ are independently selected from H, C₁₋₃ saturated alkyl, C₂₋₃ alkenyl, C₂₋₃ alkynyl and cyclopropyl, where the total number of carbon atoms in the R¹² group is no more than 5; (ie)

wherein one of R^(25a) and R^(25b) is H and the other is selected from: phenyl, which phenyl is optionally substituted by a group selected from halo, methyl, methoxy; pyridyl; and thiophenyl; and (if)

where R²⁴ is selected from: H; C₁₋₃ saturated alkyl; C₂₋₃ alkenyl; C₂₋₃ alkynyl; cyclopropyl; phenyl, which phenyl is optionally substituted by a group selected from halo, methyl, methoxy; pyridyl; and thiophenyl; when there is a single bond between C2 and C3, R² is

where R^(26a) and R^(26b) are independently selected from H, F, C₁₋₄ saturated alkyl, C₂₋₃ alkenyl, which alkyl and alkenyl groups are optionally substituted by a group selected from C₁₋₄ alkyl amido and C₁₋₄ alkyl ester; or, when one of R^(26a) and R^(26b) is H, the other is selected from nitrile and a C₁₋₄ alkyl ester; when there is a double bond between C2′ and C3′, R¹² is selected the group consisting of: (ia) C₅₋₁₀ aryl group, optionally substituted by one or more substituents selected from the group comprising: halo, nitro, cyano, ether, carboxy, ester, C₁₋₇ alkyl, C₃₋₇ heterocyclyl and bis-oxy-C₁₋₃ alkylene; (ib) C₁₋₅ saturated aliphatic alkyl; (ic) C₃₋₆ saturated cycloalkyl; (id)

wherein each of R³¹, R³² and R³³ are independently selected from H, C₁₋₃ saturated alkyl, C₂₋₃ alkenyl, C₂₋₃ alkynyl and cyclopropyl, where the total number of carbon atoms in the R¹² group is no more than 5; (ie)

wherein one of R^(35a) and R^(35b) is H and the other is selected from: phenyl, which phenyl is optionally substituted by a group selected from halo, methyl, methoxy; pyridyl; and thiophenyl; and (if)

where R²⁴ is selected from: H; C₁₋₃ saturated alkyl; C₂₋₃ alkenyl; C₂₋₃ alkynyl; cyclopropyl; phenyl, which phenyl is optionally substituted by a group selected from halo, methyl, methoxy; pyridyl; and thiophenyl; when there is a single bond between C2′ and C3′, R¹² is

where R^(36a) and R^(36b) are independently selected from H, F, C₁₋₄ saturated alkyl, C₂₋₃ alkenyl, which alkyl and alkenyl groups are optionally substituted by a group selected from C₁₋₄ alkyl amido and C₁₋₄ alkyl ester; or, when one of R^(35a) and R^(36b) is H, the other is selected from nitrile and a C₁₋₄ alkyl ester; and p is from 1 to 8.

These conjugates have been found to exhibit good activity, and suprising tolerability compared to analogous conjugates not containing the sulfonamido moiety.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows the binding of a conjugate to AXL;

FIG. 2 shows the in vivo efficacy of a conjugate;

FIG. 3 shows the in vivo efficacy of conjugates;

FIG. 4 shows the in vivo efficacy of conjugates;

FIG. 5 shows the in vivo efficacy of conjugates on a patient-derived xenograft; and

FIG. 6 shows the in vivo efficacy of conjugates on another patient-derived xenograft.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a PBD dimer with a linker connected through the N10 position on one of the PBD moieties conjugated to an antibody as defined below.

The present invention is suitable for use in providing a PBD compound to a preferred site in a subject. The conjugate allows the release of an active PBD compound that does not retain any part of the linker. There is no stub present that could affect the reactivity of the PBD compound. Thus the conjugate of formula (I) would release the compound RelA:

The specified link between the PBD dimer and the antibody in the present invention is preferably stable extracellularly. Before transport or delivery into a cell, the antibody-drug conjugate (ADC) is preferably stable and remains intact, i.e. the antibody remains linked to the drug moiety. The linkers are stable outside the target cell and may be cleaved at some efficacious rate inside the cell. An effective linker will: (i) maintain the specific binding properties of the antibody; (ii) allow intracellular delivery of the conjugate or drug moiety; (iii) remain stable and intact, i.e. not cleaved, until the conjugate has been delivered or transported to its targetted site; and (iv) maintain a cytotoxic, cell-killing effect or a cytostatic effect of the PBD drug moiety. Stability of the ADC may be measured by standard analytical techniques such as mass spectroscopy, HPLC, and the separation/analysis technique LC/MS.

Delivery of the compounds of formulae RelA is achieved at the desired activation site of the conjugate of formula (I) by the action of an enzyme, such as cathepsin, on the linking group, and in particular on the valine-alanine dipeptide moiety.

Definition Substituents

The phrase “optionally substituted” as used herein, pertains to a parent group which may be unsubstituted or which may be substituted.

Unless otherwise specified, the term “substituted” as used herein, pertains to a parent group which bears one or more substituents. The term “substituent” is used herein in the conventional sense and refers to a chemical moiety which is covalently attached to, or if appropriate, fused to, a parent group. A wide variety of substituents are well known, and methods for their formation and introduction into a variety of parent groups are also well known.

Examples of substituents are described in more detail below.

C₁₋₁₂ alkyl: The term “C₁₋₁₂ alkyl” as used herein, pertains to a monovalent moiety obtained by removing a hydrogen atom from a carbon atom of a hydrocarbon compound having from 1 to 12 carbon atoms, which may be aliphatic or alicyclic, and which may be saturated or unsaturated (e.g. partially unsaturated, fully unsaturated). The term “C₁₋₄ alkyl” as used herein, pertains to a monovalent moiety obtained by removing a hydrogen atom from a carbon atom of a hydrocarbon compound having from 1 to 4 carbon atoms, which may be aliphatic or alicyclic, and which may be saturated or unsaturated (e.g. partially unsaturated, fully unsaturated). Thus, the term “alkyl” includes the sub-classes alkenyl, alkynyl, cycloalkyl, etc., discussed below.

Examples of saturated alkyl groups include, but are not limited to, methyl (C₁), ethyl (C₂), propyl (C₃), butyl (C₄), pentyl (C₅), hexyl (C₆) and heptyl (C₇).

Examples of saturated linear alkyl groups include, but are not limited to, methyl (C₁), ethyl (C₂), n-propyl (C₃), n-butyl (C₄), n-pentyl (amyl) (C₅), n-hexyl (C₆) and n-heptyl (C₇).

Examples of saturated branched alkyl groups include iso-propyl (C₃), iso-butyl (C₄), sec-butyl (C₄), tert-butyl (C₄), iso-pentyl (C₅), and neo-pentyl (C₅).

C₂₋₁₂ Alkenyl: The term “C₂₋₁₂ alkenyl” as used herein, pertains to an alkyl group having one or more carbon-carbon double bonds.

Examples of unsaturated alkenyl groups include, but are not limited to, ethenyl (vinyl, —CH═CH₂), 1-propenyl (—CH═CH—CH₃), 2-propenyl (allyl, —CH—CH═CH₂), isopropenyl (1-methylvinyl, —C(CH₃)═CH₂), butenyl (C₄), pentenyl (C₅), and hexenyl (C₆).

C₂₋₁₂ alkynyl: The term “C₂₋₁₂ alkynyl” as used herein, pertains to an alkyl group having one or more carbon-carbon triple bonds.

Examples of unsaturated alkynyl groups include, but are not limited to, ethynyl (—C≡CH) and 2-propynyl (propargyl, —CH₂—C≡CH).

C₃₋₁₂ cycloalkyl: The term “C₃₋₁₂ cycloalkyl” as used herein, pertains to an alkyl group which is also a cyclyl group; that is, a monovalent moiety obtained by removing a hydrogen atom from an alicyclic ring atom of a cyclic hydrocarbon (carbocyclic) compound, which moiety has from 3 to 7 carbon atoms, including from 3 to 7 ring atoms.

Examples of cycloalkyl groups include, but are not limited to, those derived from:

-   -   saturated monocyclic hydrocarbon compounds:         cyclopropane (C₃), cyclobutane (C₄), cyclopentane (C₅),         cyclohexane (C₆), cycloheptane (C₇), methylcyclopropane (C₄),         dimethylcyclopropane (C₅), methylcyclobutane (C₅),         dimethylcyclobutane (C₆), methylcyclopentane (C₆),         dimethylcyclopentane (C₇) and methylcyclohexane (C₇);     -   unsaturated monocyclic hydrocarbon compounds:         cyclopropene (C₃), cyclobutene (C₄), cyclopentene (C₅),         cyclohexene (C₆), methylcyclopropene (C₄), dimethylcyclopropene         (C₅), methylcyclobutene (C₅), dimethylcyclobutene (C₆),         methylcyclopentene (C₆), dimethylcyclopentene (C₇) and         methylcyclohexene (C₇); and     -   saturated polycyclic hydrocarbon compounds:         norcarane (C₇), norpinane (C₇), norbornane (C₇).

C₃₋₂₀ heterocyclyl: The term “C3-20 heterocyclyl” as used herein, pertains to a monovalent moiety obtained by removing a hydrogen atom from a ring atom of a heterocyclic compound, which moiety has from 3 to 20 ring atoms, of which from 1 to 10 are ring heteroatoms. Preferably, each ring has from 3 to 7 ring atoms, of which from 1 to 4 are ring heteroatoms.

In this context, the prefixes (e.g. C₃₋₂₀, C₃₋₇, C₅₋₆, etc.) denote the number of ring atoms, or range of number of ring atoms, whether carbon atoms or heteroatoms. For example, the term “C₅₋₆heterocyclyl”, as used herein, pertains to a heterocyclyl group having 5 or 6 ring atoms.

Examples of monocyclic heterocyclyl groups include, but are not limited to, those derived from:

N₁: aziridine (C₃), azetidine (C₄), pyrrolidine (tetrahydropyrrole) (C₅), pyrroline (e.g., 3-pyrroline, 2,5-dihydropyrrole) (C₅), 2H-pyrrole or 3H-pyrrole (isopyrrole, isoazole) (C₅), piperidine (C₆), dihydropyridine (C₆), tetrahydropyridine (C₆), azepine (C₇); O₁: oxirane (C₃), oxetane (C₄), oxolane (tetrahydrofuran) (C₅), oxole (dihydrofuran) (C₅), oxane (tetrahydropyran) (C₆), dihydropyran (C₆), pyran (C₆), oxepin (C₇); S₁: thiirane (C₃), thietane (C₄), thiolane (tetrahydrothiophene) (C₅), thiane (tetrahydrothiopyran) (C₆), thiepane (C₇); O₂: dioxolane (C₅), dioxane (C₆), and dioxepane (C₇); O₃: trioxane (C6); N₂: imidazolidine (C₅), pyrazolidine (diazolidine) (C₅), imidazoline (C₅), pyrazoline (dihydropyrazole) (C₅), piperazine (C₆); N₁O₁: tetrahydrooxazole (C₅), dihydrooxazole (C₅), tetrahydroisoxazole (C₅), dihydroisoxazole (C₅), morpholine (C₆), tetrahydrooxazine (C₆), dihydrooxazine (C₆), oxazine (C₆); N₁S₁: thiazoline (C₅), thiazolidine (C₅), thiomorpholine (C₆); N₂O₁: oxadiazine (C₆); O₁S₁: oxathiole (C₅) and oxathiane (thioxane) (C₆); and, N₁O₁S₁: oxathiazine (C₆).

Examples of substituted monocyclic heterocyclyl groups include those derived from saccharides, in cyclic form, for example, furanoses (C₅), such as arabinofuranose, lyxofuranose, ribofuranose, and xylofuranse, and pyranoses (C₆), such as allopyranose, altropyranose, glucopyranose, mannopyranose, gulopyranose, idopyranose, galactopyranose, and talopyranose.

C₅₋₂₀ aryl: The term “C₅₋₂₀ aryl”, as used herein, pertains to a monovalent moiety obtained by removing a hydrogen atom from an aromatic ring atom of an aromatic compound, which moiety has from 3 to 20 ring atoms. The term “C₅₋₇ aryl”, as used herein, pertains to a monovalent moiety obtained by removing a hydrogen atom from an aromatic ring atom of an aromatic compound, which moiety has from 5 to 7 ring atoms and the term “C₅₋₁₀ aryl”, as used herein, pertains to a monovalent moiety obtained by removing a hydrogen atom from an aromatic ring atom of an aromatic compound, which moiety has from 5 to 10 ring atoms. Preferably, each ring has from 5 to 7 ring atoms.

In this context, the prefixes (e.g. C₃₋₂₀, C₅₋₇, C₅₋₆, C₅₋₁₀, etc.) denote the number of ring atoms, or range of number of ring atoms, whether carbon atoms or heteroatoms. For example, the term “C₅₋₆ aryl” as used herein, pertains to an aryl group having 5 or 6 ring atoms.

The ring atoms may be all carbon atoms, as in “carboaryl groups”.

Examples of carboaryl groups include, but are not limited to, those derived from benzene (i.e. phenyl) (C₆), naphthalene (C₁₀), azulene (C₁₀), anthracene (C₁₄), phenanthrene (C₁₄), naphthacene (C₁₃), and pyrene (C₁₆).

Examples of aryl groups which comprise fused rings, at least one of which is an aromatic ring, include, but are not limited to, groups derived from indane (e.g. 2,3-dihydro-1H-indene) (C), indene (C), isoindene (C), tetraline (1,2,3,4-tetrahydronaphthalene (C₁₀), acenaphthene (C₁₂), fluorene (C₁₃), phenalene (C₁₃), acephenanthrene (C₁₅), and aceanthrene (C₁₆).

Alternatively, the ring atoms may include one or more heteroatoms, as in “heteroaryl groups”. Examples of monocyclic heteroaryl groups include, but are not limited to, those derived from:

N₁: pyrrole (azole) (C₅), pyridine (azine) (C₆); O₁: furan (oxole) (C₅); S₁: thiophene (thiole) (C₅); N₁O₁: oxazole (C₅), isoxazole (C₅), isoxazine (C₆); N₂O₁: oxadiazole (furazan) (C₅); N₃O₁: oxatriazole (C₅); N₁S₁: thiazole (C₅), isothiazole (C₅); N₂: imidazole (1,3-diazole) (C₅), pyrazole (1,2-diazole) (C₅), pyridazine (1,2-diazine) (C₆), pyrimidine (1,3-diazine) (C₆) (e.g., cytosine, thymine, uracil), pyrazine (1,4-diazine) (C₆); N₃: triazole (C₅), triazine (C₆); and, N₄: tetrazole (C₅).

Examples of heteroaryl which comprise fused rings, include, but are not limited to:

-   -   C₉ (with 2 fused rings) derived from benzofuran (O₁),         isobenzofuran (O₁), indole (N₁), isoindole (N₁), indolizine         (N₁), indoline (N₁), isoindoline (N₁), purine (N₄) (e.g.,         adenine, guanine), benzimidazole (N₂), indazole (N₂),         benzoxazole (N₁O₁), benzisoxazole (N₁O₁), benzodioxole (O₂),         benzofurazan (N₂O₁), benzotriazole (N₃), benzothiofuran (S₁),         benzothiazole (N₁S₁), benzothiadiazole (N₂S);     -   C₁₀ (with 2 fused rings) derived from chromene (O₁), isochromene         (O₁), chroman (O₁), isochroman (O₁), benzodioxan (O₂), quinoline         (N₁), isoquinoline (N₁), quinolizine (N₁), benzoxazine (N₁O₁),         benzodiazine (N₂), pyridopyridine (N₂), quinoxaline (N₂),         quinazoline (N₂), cinnoline (N₂), phthalazine (N₂),         naphthyridine (N₂), pteridine (N₄);     -   C₁₁ (with 2 fused rings) derived from benzodiazepine (N₂);     -   C₁₃ (with 3 fused rings) derived from carbazole (N₁),         dibenzofuran (O₁), dibenzothiophene (S₁), carboline (N₂),         perimidine (N₂), pyridoindole (N₂); and,     -   C₁₄ (with 3 fused rings) derived from acridine (N₁), xanthene         (O₁), thioxanthene (S₁), oxanthrene (O₂), phenoxathiin (O₁S₁),         phenazine (N₂), phenoxazine (N₁O₁), phenothiazine (N₁S₁),         thianthrene (S₂), phenanthridine (N₁), phenanthroline (N₂),         phenazine (N₂).

The above groups, whether alone or part of another substituent, may themselves optionally be substituted with one or more groups selected from themselves and the additional substituents listed below.

Halo: —F, —Cl, —Br, and —I.

Hydroxy: —OH.

Ether: —OR, wherein R is an ether substituent, for example, a C₁₋₇ alkyl group (also referred to as a C alkoxy group, discussed below), a C₃₋₂₀ heterocyclyl group (also referred to as a C₃₋₂₀ heterocyclyloxy group), or a C₅₋₂₀ aryl group (also referred to as a C₅₋₂₀ aryloxy group), preferably a C₁₋₇ alkyl group.

Alkoxy: —OR, wherein R is an alkyl group, for example, a C₁₋₇ alkyl group. Examples of C₁₋₇ alkoxy groups include, but are not limited to, —OMe (methoxy), —OEt (ethoxy), —O(nPr) (n-propoxy), —O(iPr) (isopropoxy), —O(nBu) (n-butoxy), —O(sBu) (sec-butoxy), —O(iBu) (isobutoxy), and —O(tBu) (tert-butoxy).

Carboxy (carboxylic acid): —C(═O)OH.

Ester (carboxylate, carboxylic acid ester, oxycarbonyl): —C(═O)OR, wherein R is an ester substituent, for example, a C₁₋₇ alkyl group, a C₃₋₂₀ heterocyclyl group, or a C₁₋₂₀ aryl group, preferably a C₁₋₇ alkyl group. Examples of ester groups include, but are not limited to, —C(═O)OCH₃, —C(═O)OCH₂CH₃, —C(═O)OC(CH₃)₃, and —C(═O)OPh.

Amino: —NR¹R², wherein R¹ and R² are independently amino substituents, for example, hydrogen, a C₁₋₇ alkyl group (also referred to as C₁₋₇ alkylamino or di-C₁₇ alkylamino), a C₃₋₂₀ heterocyclyl group, or a C₅₋₂₀ aryl group, preferably H or a C₁₋₇ alkyl group, or, in the case of a “cyclic” amino group, R¹ and R², taken together with the nitrogen atom to which they are attached, form a heterocyclic ring having from 4 to 8 ring atoms. Amino groups may be primary (—NH₂), secondary (—NHR), or tertiary (—NHR¹R²), and in cationic form, may be quaternary (—⁺NR¹R²R³). Examples of amino groups include, but are not limited to, —NH₂, —NHCH₃, —NHC(CH₃)₂, —N(CH₃)₂, —N(CH₂CH₃)₂, and —NHPh. Examples of cyclic amino groups include, but are not limited to, aziridino, azetidino, pyrrolidino, piperidino, piperazino, morpholino, and thiomorpholino.

Amido (carbamoyl, carbamyl, aminocarbonyl, carboxamide): —C(═O)NR¹R², wherein R¹ and R² are independently amino substituents, as defined for amino groups. Examples of amido groups include, but are not limited to, —C(═O)NH₂, —C(═O)NHCH₃, —C(═O)N(CH₃)₂, —C(═O)NHCH₂CH₃, and —C(═O)N(CH₂CH₃)₂, as well as amido groups in which R¹ and R², together with the nitrogen atom to which they are attached, form a heterocyclic structure as in, for example, piperidinocarbonyl, morpholinocarbonyl, thiomorpholinocarbonyl, and piperazinocarbonyl.

Nitro: —NO₂.

Azido: —N₃.

Cyano (nitrile, carbonitrile): —CN.

Antibody

In one aspect the antibody is an antibody that binds to AXL.

1H12

In some embodiments the antibody comprises a VH domain having a VH CDR3 with the amino acid sequence of SEQ ID NO.7. In some embodiments the VH domain further comprises a VH CDR2 with the amino acid sequence of SEQ ID NO.6, and/or a VH CDR1 with the amino acid sequence of SEQ ID NO.5. In some embodiments the the antibody comprises a VH domain having a VH CDR1 with the amino acid sequence of SEQ ID NO.5, a VH CDR2 with the amino acid sequence of SEQ ID NO.6, and a VH CDR3 with the amino acid sequence of SEQ ID NO.7. In preferred embodiments the antibody comprises a VH domain having the sequence according to SEQ ID NO. 1.

The antibody may further comprise a VL domain. In some embodiments the antibody comprises a VL domain having a VL CDR3 with the amino acid sequence of SEQ ID NO.10. In some embodiments the VL domain further comprises a VL CDR2 with the amino acid sequence of SEQ ID NO.9, and/or a VL CDR1 with the amino acid sequence of SEQ ID NO.8. In some embodiments the the antibody comprises a VL domain having a VL CDR1 with the amino acid sequence of SEQ ID NO.8, a VL CDR2 with the amino acid sequence of SEQ ID NO.9, and a VL CDR3 with the amino acid sequence of SEQ ID NO.10. In preferred embodiments the antibody comprises a VL domain having the sequence according to SEQ ID NO. 2.

In preferred embodiments the antibody comprises a VH domain and a VL domain. Preferably the VH comprises the sequence of SEQ ID NO.1 and the VL domain comprises the sequence of SEQ ID NO.2.

The VH and VL domain(s) may pair so as to form an antibody antigen binding site that binds AXL.

In some embodiments the antibody is an intact antibody comprising a VH domain paired with a VL domain, the VH and VL domains having sequences of SEQ ID NO.1 paired with SEQ ID NO.2.

In some embodiments the antibody comprises a heavy chain having the sequence of SEQ ID NO. 3 paired with a light chain having the sequence of SEQ ID NO.4. In some embodiments the antibody is an intact antibody comprising two heavy chains having the sequence of SEQ ID NO.3, each paired with a light chain having the sequence of SEQ ID NO.4.

In some embodiments the antibody comprises a heavy chain having the sequence of SEQ ID NO. 24 paired with a light chain having the sequence of SEQ ID NO.4. In some embodiments the antibody is an intact antibody comprising two heavy chains having the sequence of SEQ ID NO.24, each paired with a light chain having the sequence of SEQ ID NO.4.

In one aspect the antibody is an antibody as described herein which has been modified (or further modified) as described below. In some embodiments the antibody is a humanised, deimmunised or resurfaced version of an antibody disclosed herein.

5F11

In some embodiments the antibody comprises a VH domain having a VH CDR3 with the amino acid sequence of SEQ ID NO.15. In some embodiments the VH domain further comprises a VH CDR2 with the amino acid sequence of SEQ ID NO.14, and/or a VH CDR1 with the amino acid sequence of SEQ ID NO.13. In some embodiments the the antibody comprises a VH domain having a VH CDR1 with the amino acid sequence of SEQ ID NO.13, a VH CDR2 with the amino acid sequence of SEQ ID NO.14, and a VH CDR3 with the amino acid sequence of SEQ ID NO.15.

In some embodiments the antibody comprises a VH domain having the sequence according to SEQ ID NO. 11. In some embodiments the antibody comprises a VH domain having the sequence according to SEQ ID NO. 19. In some embodiments the antibody comprises a VH domain having the sequence according to SEQ ID NO. 20. In some embodiments the antibody comprises a VH domain having the sequence according to SEQ ID NO. 21.

The antibody may further comprise a VL domain. In some embodiments the antibody comprises a VL domain having a VL CDR3 with the amino acid sequence of SEQ ID NO.18. In some embodiments the VL domain further comprises a VL CDR2 with the amino acid sequence of SEQ ID NO.17, and/or a VL CDR1 with the amino acid sequence of SEQ ID NO.16. In some embodiments the the antibody comprises a VL domain having a VL CDR1 with the amino acid sequence of SEQ ID NO.16, a VL CDR2 with the amino acid sequence of SEQ ID NO.17, and a VL CDR3 with the amino acid sequence of SEQ ID NO.18.

In some embodiments the antibody comprises a VL domain having the sequence according to SEQ ID NO. 22.

In preferred embodiments the antibody comprises a VH domain and a VL domain. In some embodiments the VH comprises a VH CDR1 with the amino acid sequence of SEQ ID NO.13, a VH CDR2 with the amino acid sequence of SEQ ID NO.14, and a VH CDR3 with the amino acid sequence of SEQ ID NO.15; and the VL domain comprises a VL CDR1 with the amino acid sequence of SEQ ID NO.16, a VL CDR2 with the amino acid sequence of SEQ ID NO.17, and a VL CDR3 with the amino acid sequence of SEQ ID NO.18.

In some embodiments the antibody comprises a VH domain having the sequence of SEQ ID NO.19 and the VL domain having the sequence of SEQ ID NO.22. In some embodiments the antibody comprises a VH domain having the sequence of SEQ ID NO.20 and the VL domain having the sequence of SEQ ID NO.22. In some embodiments the antibody comprises a VH domain having the sequence of SEQ ID NO.21 and the VL domain having the sequence of SEQ ID NO.22.

The VH and VL domain(s) may pair so as to form an antibody antigen binding site that binds AXL.

In some embodiments the antibody is an intact antibody comprising a VH domain paired with a VL domain.

In one aspect the antibody is an antibody as described herein which has been modified (or further modified) as described below. In some embodiments the antibody is a humanised, deimmunised or resurfaced version of an antibody disclosed herein.

Terminology

The term “antibody” herein is used in the broadest sense and specifically covers monoclonal antibodies, polyclonal antibodies, dimers, multimers, multispecific antibodies (e.g., bispecific antibodies), intact antibodies and antibody fragments, so long as they exhibit the desired biological activity, for example, the ability to bind AXL. Antibodies may be murine, human, humanized, chimeric, or derived from other species. An antibody is a protein generated by the immune system that is capable of recognizing and binding to a specific antigen. (Janeway, C., Travers, P., Walport, M., Shlomchik (2001) Immuno Biology, 5th Ed., Garland Publishing, New York). A target antigen generally has numerous binding sites, also called epitopes, recognized by CDRs on multiple antibodies. Each antibody that specifically binds to a different epitope has a different structure. Thus, one antigen may have more than one corresponding antibody. An antibody includes a full-length immunoglobulin molecule or an immunologically active portion of a full-length immunoglobulin molecule, i.e., a molecule that contains an antigen binding site that immunospecifically binds an antigen of a target of interest or part thereof, such targets including but not limited to, cancer cell or cells that produce autoimmune antibodies associated with an autoimmune disease. The immunoglobulin can be of any type (e.g. IgG, IgE, IgM, IgD, and IgA), class (e.g. IgG1, IgG2, IgG3, IgG4, IgA1 and IgA2) or subclass, or allotype (e.g. human G1m1, G1m2, G1m3, non-G1m1 [that, is any allotype other than G1m1], G1m17, G2m23, G3m21, G3m28, G3m11, G3m5, G3m13, G3m14, G3m10, G3m15, G3m16, G3m6, G3m24, G3m26, G3m27, A2m1, A2m2, Km1, Km2 and Km3) of immunoglobulin molecule. The immunoglobulins can be derived from any species, including human, murine, or rabbit origin.

As used herein, “binds AXL” is used to mean the antibody binds AXL with a higher affinity than a non-specific partner such as Bovine Serum Albumin (BSA, Genbank accession no. CAA76847, version no. CAA76847.1 GI:3336842, record update date: Jan. 7, 2011 02:30 PM). In some embodiments the antibody binds AXL with an association constant (K_(a)) at least 2, 3, 4, 5, 10, 20, 50, 100, 200, 500, 1000, 2000, 5000, 104, 10⁵ or 10⁶-fold higher than the antibody's association constant for BSA, when measured at physiological conditions. The antibodies of the invention can bind CD22 with a high affinity. For example, in some embodiments the antibody can bind CD22 with a K_(D) equal to or less than about 10⁻⁶ M, such as 1×10⁻⁶, 10⁻⁷, 10⁻⁸, 10⁻⁹, 10⁻¹⁰, 10⁻¹¹, 10⁻¹², 10⁻¹³ or 10⁻¹⁴.

AXL is member of the human TAM family of receptor tyrosine kinases. In some embodiments, the AXL polypeptide corresponds to Genbank accession no. AAH32229, version no. AAH32229.1 GI:21619004, record update date: Mar. 6, 2012 01:18 PM (SEQ ID NO.9). In one embodiment, the nucleic acid encoding AXL polypeptide corresponds to Genbank accession no. M76125, version no. M76125.1 GI:292869, record update date: Jun. 23, 2010 08:53 AM. In some embodiments, the AXL polypeptide has the sequence of SEQ ID NO.23.

“Antibody fragments” comprise a portion of a full length antibody, generally the antigen binding or variable region thereof. Examples of antibody fragments include Fab, Fab′, F(ab′)₂, and scFv fragments; diabodies; linear antibodies; fragments produced by a Fab expression library, anti-idiotypic (anti-Id) antibodies, CDR (complementary determining region), and epitope-binding fragments of any of the above which immunospecifically bind to cancer cell antigens, viral antigens or microbial antigens, single-chain antibody molecules; and multispecific antibodies formed from antibody fragments.

The term “monoclonal antibody” as used herein refers to an antibody obtained from a population of substantially homogeneous antibodies, i.e. the individual antibodies comprising the population are identical except for possible naturally occurring mutations that may be present in minor amounts. Monoclonal antibodies are highly specific, being directed against a single antigenic site. Furthermore, in contrast to polyclonal antibody preparations which include different antibodies directed against different determinants (epitopes), each monoclonal antibody is directed against a single determinant on the antigen. In addition to their specificity, the monoclonal antibodies are advantageous in that they may be synthesized uncontaminated by other antibodies. The modifier “monoclonal” indicates the character of the antibody as being obtained from a substantially homogeneous population of antibodies, and is not to be construed as requiring production of the antibody by any particular method. For example, the monoclonal antibodies to be used in accordance with the present invention may be made by the hybridoma method first described by Kohler et al (1975) Nature 256:495, or may be made by recombinant DNA methods (see, U.S. Pat. No. 4,816,567). The monoclonal antibodies may also be isolated from phage antibody libraries using the techniques described in Clackson et al. (1991) Nature, 352:624-628; Marks et al. (1991) J. Mol. Biol., 222:581-597 or from transgenic mice carrying a fully human immunoglobulin system (Lonberg (2008) Curr. Opinion 20(4):450-459).

The monoclonal antibodies herein specifically include “chimeric” antibodies in which a portion of the heavy and/or light chain is identical with or homologous to corresponding sequences in antibodies derived from a particular species or belonging to a particular antibody class or subclass, while the remainder of the chain(s) is identical with or homologous to corresponding sequences in antibodies derived from another species or belonging to another antibody class or subclass, as well as fragments of such antibodies, so long as they exhibit the desired biological activity (U.S. Pat. No. 4,816,567; and Morrison et al (1984) Proc. Natl. Acad. Sci. USA, 81:6851-6855). Chimeric antibodies include “primatized” antibodies comprising variable domain antigen-binding sequences derived from a non-human primate (e.g. Old World Monkey or Ape) and human constant region sequences.

An “intact antibody” herein is one comprising VL and VH domains, as well as a light chain constant domain (CL) and heavy chain constant domains, CH1, CH2 and CH3. The constant domains may be native sequence constant domains (e.g. human native sequence constant domains) or amino acid sequence variant thereof. The intact antibody may have one or more “effector functions” which refer to those biological activities attributable to the Fc region (a native sequence Fc region or amino acid sequence variant Fc region) of an antibody. Examples of antibody effector functions include C1q binding; complement dependent cytotoxicity; Fc receptor binding; antibody-dependent cell-mediated cytotoxicity (ADCC); phagocytosis; and down regulation of cell surface receptors such as B cell receptor and BCR.

Depending on the amino acid sequence of the constant domain of their heavy chains, intact antibodies can be assigned to different “classes.” There are five major classes of intact antibodies: IgA, IgD, IgE, IgG, and IgM, and several of these may be further divided into “subclasses” (isotypes), e.g., IgG1, IgG2, IgG3, IgG4, IgA, and IgA2. The heavy-chain constant domains that correspond to the different classes of antibodies are called α, δ, ε, γ, and μ, respectively. The subunit structures and three-dimensional configurations of different classes of immunoglobulins are well known.

Modification of Antibodies

The antibodies disclosed herein may be modified. For example, to make them less immunogenic to a human subject. This may be achieved using any of a number of techniques familiar to the person skilled in the art. Some of these techniques are described in more detail below.

Humanisation

Techniques to reduce the in vivo immunogenicity of a non-human antibody or antibody fragment include those termed “humanisation”.

A “humanized antibody” refers to a polypeptide comprising at least a portion of a modified variable region of a human antibody wherein a portion of the variable region, preferably a portion substantially less than the intact human variable domain, has been substituted by the corresponding sequence from a non-human species and wherein the modified variable region is linked to at least another part of another protein, preferably the constant region of a human antibody. The expression “humanized antibodies” includes human antibodies in which one or more complementarity determining region (“CDR”) amino acid residues and/or one or more framework region (“FW” or “FR”) amino acid residues are substituted by amino acid residues from analogous sites in rodent or other non-human antibodies. The expression “humanized antibody” also includes an immunoglobulin amino acid sequence variant or fragment thereof that comprises an FR having substantially the amino acid sequence of a human immunoglobulin and a CDR having substantially the amino acid sequence of a non-human immunoglobulin.

“Humanized” forms of non-human (e.g., murine) antibodies are chimeric antibodies that contain minimal sequence derived from non-human immunoglobulin. Or, looked at another way, a humanized antibody is a human antibody that also contains selected sequences from non-human (e.g. murine) antibodies in place of the human sequences. A humanized antibody can include conservative amino acid substitutions or non-natural residues from the same or different species that do not significantly alter its binding and/or biologic activity. Such antibodies are chimeric antibodies that contain minimal sequence derived from non-human immunoglobulins.

There are a range of humanisation techniques, including ‘CDR grafting’, ‘guided selection’, ‘deimmunization’, ‘resurfacing’ (also known as ‘veneering’), ‘composite antibodies’, ‘Human String Content Optimisation’ and framework shuffling.

CDR Grafting

In this technique, the humanized antibodies are human immunoglobulins (recipient antibody) in which residues from a complementary-determining region (CDR) of the recipient antibody are replaced by residues from a CDR of a non-human species (donor antibody) such as mouse, rat, camel, bovine, goat, or rabbit having the desired properties (in effect, the non-human CDRs are ‘grafted’ onto the human framework). In some instances, framework region (FR) residues of the human immunoglobulin are replaced by corresponding non-human residues (this may happen when, for example, a particular FR residue has significant effect on antigen binding).

Furthermore, humanized antibodies can comprise residues that are found neither in the recipient antibody nor in the imported CDR or framework sequences. These modifications are made to further refine and maximize antibody performance. Thus, in general, a humanized antibody will comprise all of at least one, and in one aspect two, variable domains, in which all or all of the hypervariable loops correspond to those of a non-human immunoglobulin and all or substantially all of the FR regions are those of a human immunoglobulin sequence. The humanized antibody optionally also will comprise at least a portion of an immunoglobulin constant region (Fc), or that of a human immunoglobulin.

Guided Selection

The method consists of combining the V_(H) or V_(L) domain of a given non-human antibody specific for a particular epitope with a human V_(H) or V_(L) library and specific human V domains are selected against the antigen of interest. This selected human VH is then combined with a VL library to generate a completely human VHxVL combination. The method is described in Nature Biotechnology (N.Y.) 12, (1994) 899-903.

Composite Antibodies

In this method, two or more segments of amino acid sequence from a human antibody are combined within the final antibody molecule. They are constructed by combining multiple human VH and VL sequence segments in combinations which limit or avoid human T cell epitopes in the final composite antibody V regions. Where required, T cell epitopes are limited or avoided by, exchanging V region segments contributing to or encoding a T cell epitope with alternative segments which avoid T cell epitopes. This method is described in US 2008/0206239 A1.

Deimmunization

This method involves the removal of human (or other second species) T-cell epitopes from the V regions of the therapeutic antibody (or other molecule). The therapeutic antibodies V-region sequence is analysed for the presence of MHC class II-binding motifs by, for example, comparison with databases of MHC-binding motifs (such as the “motifs” database hosted at www.wehi.edu.au). Alternatively, MHC class II-binding motifs may be identified using computational threading methods such as those devised by Altuvia et al. (J. Mol. Biol. 249 244-250 (1995)); in these methods, consecutive overlapping peptides from the V-region sequences are testing for their binding energies to MHC class II proteins. This data can then be combined with information on other sequence features which relate to successfully presented peptides, such as amphipathicity, Rothbard motifs, and cleavage sites for cathepsin B and other processing enzymes.

Once potential second species (e.g. human) T-cell epitopes have been identified, they are eliminated by the alteration of one or more amino acids. The modified amino acids are usually within the T-cell epitope itself, but may also be adjacent to the epitope in terms of the primary or secondary structure of the protein (and therefore, may not be adjacent in the primary structure). Most typically, the alteration is by way of substitution but, in some circumstances amino acid addition or deletion will be more appropriate.

All alterations can be accomplished by recombinant DNA technology, so that the final molecule may be prepared by expression from a recombinant host using well established methods such as Site Directed Mutagenesis. However, the use of protein chemistry or any other means of molecular alteration is also possible.

Resurfacing

This method involves:

-   -   (a) determining the conformational structure of the variable         region of the non-human (e.g. rodent) antibody (or fragment         thereof) by constructing a three-dimensional model of the         non-human antibody variable region;     -   (b) generating sequence alignments using relative accessibility         distributions from x-ray crystallographic structures of a         sufficient number of non-human and human antibody variable         region heavy and light chains to give a set of heavy and light         chain framework positions wherein the alignment positions are         identical in 98% of the sufficient number of non-human antibody         heavy and light chains;     -   (c) defining for the non-human antibody to be humanized, a set         of heavy and light chain surface exposed amino acid residues         using the set of framework positions generated in step (b);     -   (d) identifying from human antibody amino acid sequences a set         of heavy and light chain surface exposed amino acid residues         that is most closely identical to the set of surface exposed         amino acid residues defined in step (c), wherein the heavy and         light chain from the human antibody are or are not naturally         paired;     -   (e) substituting, in the amino acid sequence of the non-human         antibody to be humanized, the set of heavy and light chain         surface exposed amino acid residues defined in step (c) with the         set of heavy and light chain surface exposed amino acid residues         identified in step (d);     -   (f) constructing a three-dimensional model of the variable         region of the non-human antibody resulting from the substituting         specified in step (e);     -   (g) identifying, by comparing the three-dimensional models         constructed in steps (a) and (f), any amino acid residues from         the sets identified in steps (c) or (d), that are within 5         Angstroms of any atom of any residue of the complementarity         determining regions of the non-human antibody to be humanized;         and     -   (h) changing any residues identified in step (g) from the human         to the original non-human amino acid residue to thereby define a         non-human antibody humanizing set of surface exposed amino acid         residues; with the proviso that step (a) need not be conducted         first, but must be conducted prior to step (g).

Superhumanization

The method compares the non-human sequence with the functional human germline gene repertoire. Those human genes encoding canonical structures identical or closely related to the non-human sequences are selected. Those selected human genes with highest homology within the CDRs are chosen as FR donors. Finally, the non-human CDRs are grafted onto these human FRs. This method is described in patent WO 2005/079479 A2.

Human String Content Optimization

This method compares the non-human (e.g. mouse) sequence with the repertoire of human germline genes and the differences are scored as Human String Content (HSC) that quantifies a sequence at the level of potential MHC/T-cell epitopes. The target sequence is then humanized by maximizing its HSC rather than using a global identity measure to generate multiple diverse humanized variants (described in Molecular Immunology, 44, (2007) 1986-1998).

Framework Shuffling

The CDRs of the non-human antibody are fused in-frame to cDNA pools encompassing all known heavy and light chain human germline gene frameworks. Humanised antibodies are then selected by e.g. panning of the phage displayed antibody library. This is described in Methods 36, 43-60 (2005).

Modification of Antibody with Azide

The antibody may prepared for conjugation with the drug linker through a three step process:

-   -   (1) Expression of antibody (Ab) bearing the core N-glycan in a         suitable expression system (e.g. a CHO cell line). The core         N-glycan is typically conjugated to Asn-297 of the heavy chain         according to the numbering system of Kabat;     -   (2) trimming of all glycan isoforms (complex, hybrid,         high-mannose) with an endoglycosidase to leave the core GlcNAc;         and     -   (3) enzymatic transfer to the core GlcNAc of a N-acetylgalactose         residue harboring an azide group for conjugation to the drug         linker.

An overview of the above process is set out in van Geel, R., et al., Bioconjugate Chemistry, 2015, 26, 2233-2242; DOI: 10.1021/acs.bioconjchem.5b00224. Alternatively, a one-pot process may be used—see the examples.

Embodiments X

In some embodiments, X is a single bond.

In other embodiments, X is —CH₂—.

In further embodiments, X is —C₂H₄—.

In some embodiments, n is 1 to 4.

In some of these embodiments, n is 1.

In other of these embodiments, n is 2.

In further of these embodiments, n is 4.

R⁷

In one embodiment, R⁷ is methyl.

In another embodiment, R⁷ is phenyl.

R²

When there is a double bond present between C2 and C3, R² is selected from:

(a) C₅₋₁₀ aryl group, optionally substituted by one or more substituents selected from the group comprising: halo, nitro, cyano, ether, C₁₋₇ alkyl, C₃₋₇ heterocyclyl and bis-oxy-C₁₋₃ alkylene; (b) C₁₋₅ saturated aliphatic alkyl; (c) C₃ saturated cycloalkyl; (d)

wherein each of R²¹, R²² and R²³ are independently selected from H, C₁₋₃ saturated alkyl, C₂₋₃ alkenyl, C₂₋₃ alkynyl and cyclopropyl, where the total number of carbon atoms in the R² group is no more than 5; (e)

wherein one of R^(25a) and R^(25b) is H and the other is selected from: phenyl, which phenyl is optionally substituted by a group selected from halo methyl, methoxy; pyridyl; and thiophenyl; and (f)

where R²⁴ is selected from: H; C₁₋₃ saturated alkyl; C₂₋₃ alkenyl; C₂₋₃ alkynyl; cyclopropyl; phenyl, which phenyl is optionally substituted by a group selected from halo methyl, methoxy; pyridyl; and thiophenyl.

When R² is a C₅₋₁₀ aryl group, it may be a C₅₋₇ aryl group. A C₅₋₇ aryl group may be a phenyl group or a C₅₋₇ heteroaryl group, for example furanyl, thiophenyl and pyridyl. In some embodiments, R² is preferably phenyl. In other embodiments, R¹² is preferably thiophenyl, for example, thiophen-2-yl and thiophen-3-yl.

When R² is a C₅₋₁₀ aryl group, it may be a C₈₋₁₀ aryl, for example a quinolinyl or isoquinolinyl group. The quinolinyl or isoquinolinyl group may be bound to the PBD core through any available ring position. For example, the quinolinyl may be quinolin-2-yl, quinolin-3-yl, quinolin-4yl, quinolin-5-yl, quinolin-6-yl, quinolin-7-yl and quinolin-8-yl. Of these quinolin-3-yl and quinolin-6-yl may be preferred. The isoquinolinyl may be isoquinolin-1-yl, isoquinolin-3-yl, isoquinolin-4yl, isoquinolin-5-yl, isoquinolin-6-yl, isoquinolin-7-yl and isoquinolin-8-yl. Of these isoquinolin-3-yl and isoquinolin-6-yl may be preferred.

When R² is a C₅₋₁₀ aryl group, it may bear any number of substituent groups. It preferably bears from 1 to 3 substituent groups, with 1 and 2 being more preferred, and singly substituted groups being most preferred. The substituents may be any position.

Where R² is C₅₋₇ aryl group, a single substituent is preferably on a ring atom that is not adjacent the bond to the remainder of the compound, i.e. it is preferably β or γ to the bond to the remainder of the compound. Therefore, where the C₅₋₇ aryl group is phenyl, the substituent is preferably in the meta- or para-positions, and more preferably is in the para-position.

Where R² is a C3-10 aryl group, for example quinolinyl or isoquinolinyl, it may bear any number of substituents at any position of the quinoline or isoquinoline rings. In some embodiments, it bears one, two or three substituents, and these may be on either the proximal and distal rings or both (if more than one substituent).

R² Substituents, when R² is a C₅₋₁₀ Aryl Group

If a substituent on R² when R² is a C₅₋₁₀ aryl group is halo, it is preferably F or Cl, more preferably Cl.

If a substituent on R² when R² is a C₅₋₁₀ aryl group is ether, it may in some embodiments be an alkoxy group, for example, a C₁₋₇ alkoxy group (e.g. methoxy, ethoxy) or it may in some embodiments be a C₅₋₇ aryloxy group (e.g phenoxy, pyridyloxy, furanyloxy). The alkoxy group may itself be further substituted, for example by an amino group (e.g. dimethylamino).

If a substituent on R² when R² is a C₅₋₁₀ aryl group is C₁₋₇ alkyl, it may preferably be a C₁₋₄ alkyl group (e.g. methyl, ethyl, propryl, butyl).

If a substituent on R² when R² is a C₅₋₁₀ aryl group is C₃₋₇ heterocyclyl, it may in some embodiments be C₆ nitrogen containing heterocyclyl group, e.g. morpholino, thiomorpholino, piperidinyl, piperazinyl. These groups may be bound to the rest of the PBD moiety via the nitrogen atom. These groups may be further substituted, for example, by C₁₋₄ alkyl groups. If the C₆ nitrogen containing heterocyclyl group is piperazinyl, the said further substituent may be on the second nitrogen ring atom.

If a substituent on R² when R² is a C₅₋₁₀ aryl group is bis-oxy-C₁₋₃ alkylene, this is preferably bis-oxy-methylene or bis-oxy-ethylene.

If a substituent on R² when R² is a C₅₋₁₀ aryl group is ester, this is preferably methyl ester or ethyl ester.

Particularly preferred substituents when R² is a C₅₋₁₀ aryl group include methoxy, ethoxy, fluoro, chloro, cyano, bis-oxy-methylene, methyl-piperazinyl, morpholino and methylthiophenyl. Other particularly preferred substituent for R² are dimethylaminopropyloxy and carboxy.

Particularly preferred substituted R² groups when R² is a C₅₋₁₀ aryl group include, but are not limited to, 4-methoxy-phenyl, 3-methoxyphenyl, 4-ethoxy-phenyl, 3-ethoxy-phenyl, 4-fluoro-phenyl, 4-chloro-phenyl, 3,4-bisoxymethylene-phenyl, 4-methylthiophenyl, 4-cyanophenyl, 4-phenoxyphenyl, quinolin-3-yl and quinolin-6-yl, isoquinolin-3-yl and isoquinolin-6-yl, 2-thienyl, 2-furanyl, methoxynaphthyl, and naphthyl. Another possible substituted R² group is 4-nitrophenyl. R² groups of particular interest include 4-(4-methylpiperazin-1-yl)phenyl and 3,4-bisoxymethylene-phenyl.

When R² is C₁₋₅ saturated aliphatic alkyl, it may be methyl, ethyl, propyl, butyl or pentyl. In some embodiments, it may be methyl, ethyl or propyl (n-pentyl or isopropyl). In some of these embodiments, it may be methyl. In other embodiments, it may be butyl or pentyl, which may be linear or branched.

When R² is C₃₋₆ saturated cycloalkyl, it may be cyclopropyl, cyclobutyl, cyclopentyl or cyclohexyl. In some embodiments, it may be cyclopropyl.

When R² is

each of R²¹, R²² and R²³ are independently selected from H, C₁₋₃ saturated alkyl, C₂₋₃ alkenyl, C₂₋₃ alkynyl and cyclopropyl, where the total number of carbon atoms in the R² group is no more than 5. In some embodiments, the total number of carbon atoms in the R² group is no more than 4 or no more than 3.

In some embodiments, one of R²¹, R²² and R²³ is H, with the other two groups being selected from H, C₁₋₃ saturated alkyl, C₂₋₃ alkenyl, C₂₋₃ alkynyl and cyclopropyl.

In other embodiments, two of R²¹, R²² and R²³ are H, with the other group being selected from H, C₁₋₃ saturated alkyl, C₂₋₃ alkenyl, C₂₋₃ alkynyl and cyclopropyl.

In some embodiments, the groups that are not H are selected from methyl and ethyl. In some of these embodiments, the groups that are not H are methyl.

In some embodiments, R²¹ is H.

In some embodiments, R²² is H.

In some embodiments, R²³ is H.

In some embodiments, R²¹ and R²² are H.

In some embodiments, R²¹ and R²³ are H.

In some embodiments, R²² and R²³ are H.

A R² group of particular interest is:

When R² is

one of R^(25a) and R^(25b) is H and the other is selected from: phenyl, which phenyl is optionally substituted by a group selected from halo, methyl, methoxy; pyridyl; and thiophenyl. In some embodiments, the group which is not H is optionally substituted phenyl. If the phenyl optional substituent is halo, it is preferably fluoro. In some embodiment, the phenyl group is unsubstituted.

When R² is

R²⁴ is selected from: H; C₁₋₃ saturated alkyl; C₂₋₃ alkenyl; C₂₋₃ alkynyl; cyclopropyl; phenyl, which phenyl is optionally substituted by a group selected from halo methyl, methoxy; pyridyl; and thiophenyl. If the phenyl optional substituent is halo, it is preferably fluoro. In some embodiment, the phenyl group is unsubstituted.

In some embodiments, R²⁴ is selected from H, methyl, ethyl, ethenyl and ethynyl. In some of these embodiments, R²⁴ is selected from H and methyl.

When there is a single bond present between C2 and C3,

R² is

where R^(26a) and R^(26b) are independently selected from H, F, C₁₋₄ saturated alkyl, C₂₋₃ alkenyl, which alkyl and alkenyl groups are optionally substituted by a group selected from C₁₋₄ alkyl amido and C₁₋₄ alkyl ester; or, when one of R^(26a) and R^(26b) is H, the other is selected from nitrile and a C₁₋₄ alkyl ester.

In some embodiments, it is preferred that R^(26a) and R^(26b) are both H.

In other embodiments, it is preferred that R^(26a) and R^(26b) are both methyl.

In further embodiments, it is preferred that one of R^(26a) and R^(26b) is H, and the other is selected from C₁₋₄ saturated alkyl, C₂₋₃ alkenyl, which alkyl and alkenyl groups are optionally substituted. In these further embodiment, it may be further preferred that the group which is not H is selected from methyl and ethyl.

R¹²

The above preferences for R² apply equally to R¹².

In one embodiment of the invention, DL is

Drug Loading

The drug loading is the average number of PBD drugs per antibody, e.g. antibody.

The average number of drugs per antibody in preparations of ADC from conjugation reactions may be characterized by conventional means such as UV, reverse phase HPLC, HIC, mass spectroscopy, ELISA assay, and electrophoresis. The quantitative distribution of ADC in terms of p may also be determined. By ELISA, the averaged value of p in a particular preparation of ADC may be determined (Hamblett et al (2004) Clin. Cancer Res. 10:7063-7070; Sanderson et al (2005) Clin. Cancer Res. 11:843-852). However, the distribution of p (drug) values is not discernible by the antibody-antigen binding and detection limitation of ELISA. Also, ELISA assay for detection of antibody-drug conjugates does not determine where the drug moieties are attached to the antibody, such as the heavy chain or light chain fragments, or the particular amino acid residues. In some instances, separation, purification, and characterization of homogeneous ADC where p is a certain value from ADC with other drug loadings may be achieved by means such as reverse phase HPLC or electrophoresis. Such techniques are also applicable to other types of conjugates.

For the present antibody-drug conjugates, p is limited by the number of attachment sites on the antibody, i.e. the number of azide groups. For example, the antibody may have only one or two azide groups to which the drug linker may be attached.

Typically, fewer than the theoretical maximum of drug moieties are conjugated to an antibody during a conjugation reaction. The loading (drug/antibody ratio) of an ADC may be controlled in several different manners, including: (i) limiting the molar excess of drug-linker intermediate (D-L) or linker reagent relative to antibody, and (ii) limiting the conjugation reaction time or temperature.

Where more than one nucleophilic or electrophilic group of the antibody reacts with a drug-linker intermediate, or linker reagent followed by drug moiety reagent, then the resulting product is a mixture of ADC compounds with a distribution of drug moieties attached to an antibody, e.g. 1, 2, 3, etc. Liquid chromatography methods such as polymeric reverse phase (PLRP) and hydrophobic interaction (HIC) may separate compounds in the mixture by drug loading value. Preparations of ADC with a single drug loading value (p) may be isolated, however, these single loading value ADCs may still be heterogeneous mixtures because the drug moieties may be attached, via the linker, at different sites on the antibody.

Thus the antibody-drug conjugate compositions of the invention include mixtures of antibody-drug conjugate compounds where the antibody has one or more PBD drug moieties and where the drug moieties may be attached to the antibody at various amino acid residues.

In one embodiment, the average number of dimer pyrrolobenzodiazepine groups per antibody is in the range 1 to 8. In some embodiments the range is selected from 1 to 4, 1 to 4, 2 to 4, and 1 to 3.

In some embodiments, there are one or two dimer pyrrolobenzodiazepine groups per antibody.

Includes Other Forms

Unless otherwise specified, included in the above are the well known ionic, salt, solvate, and protected forms of these substituents. For example, a reference to carboxylic acid (—COOH) also includes the anionic (carboxylate) form (—COO⁻), a salt or solvate thereof, as well as conventional protected forms. Similarly, a reference to an amino group includes the protonated form (—N⁺HR¹R²), a salt or solvate of the amino group, for example, a hydrochloride salt, as well as conventional protected forms of an amino group. Similarly, a reference to a hydroxyl group also includes the anionic form (—O⁻), a salt or solvate thereof, as well as conventional protected forms.

Salts

It may be convenient or desirable to prepare, purify, and/or handle a corresponding salt of the active compound, for example, a pharmaceutically-acceptable salt. Examples of pharmaceutically acceptable salts are discussed in Berge, et al., J. Pharm. Sci., 66, 1-19 (1977).

For example, if the compound is anionic, or has a functional group which may be anionic (e.g. —COOH may be —COO⁻), then a salt may be formed with a suitable cation. Examples of suitable inorganic cations include, but are not limited to, alkali metal ions such as Na⁺ and K⁺, alkaline earth cations such as Ca²⁺ and Mg²⁺, and other cations such as Al⁺³. Examples of suitable organic cations include, but are not limited to, ammonium ion (i.e. NH₄ ⁺) and substituted ammonium ions (e.g. NH₃R⁺, NH₂R₂ ⁺, NHR₃ ⁺, NR₄ ⁺). Examples of some suitable substituted ammonium ions are those derived from: ethylamine, diethylamine, dicyclohexylamine, triethylamine, butylamine, ethylenediamine, ethanolamine, diethanolamine, piperazine, benzylamine, phenylbenzylamine, choline, meglumine, and tromethamine, as well as amino acids, such as lysine and arginine. An example of a common quaternary ammonium ion is N(CH₃)₄ ⁺.

If the compound is cationic, or has a functional group which may be cationic (e.g. —NH₂ may be —NH₃ ⁺), then a salt may be formed with a suitable anion. Examples of suitable inorganic anions include, but are not limited to, those derived from the following inorganic acids: hydrochloric, hydrobromic, hydroiodic, sulfuric, sulfurous, nitric, nitrous, phosphoric, and phosphorous.

Examples of suitable organic anions include, but are not limited to, those derived from the following organic acids: 2-acetyoxybenzoic, acetic, ascorbic, aspartic, benzoic, camphorsulfonic, cinnamic, citric, edetic, ethanedisulfonic, ethanesulfonic, fumaric, glucheptonic, gluconic, glutamic, glycolic, hydroxymaleic, hydroxynaphthalene carboxylic, isethionic, lactic, lactobionic, lauric, maleic, malic, methanesulfonic, mucic, oleic, oxalic, palmitic, pamoic, pantothenic, phenylacetic, phenylsulfonic, propionic, pyruvic, salicylic, stearic, succinic, sulfanilic, tartaric, toluenesulfonic, trifluoroacetic acid and valeric. Examples of suitable polymeric organic anions include, but are not limited to, those derived from the following polymeric acids: tannic acid, carboxymethyl cellulose.

Solvates

It may be convenient or desirable to prepare, purify, and/or handle a corresponding solvate of the active compound. The term “solvate” is used herein in the conventional sense to refer to a complex of solute (e.g. active compound, salt of active compound) and solvent. If the solvent is water, the solvate may be conveniently referred to as a hydrate, for example, a mono-hydrate, a di-hydrate, a tri-hydrate, etc.

The invention includes compounds where a solvent adds across the imine bond of the PBD moiety, which is illustrated below where the solvent is water or an alcohol (R^(A)OH, where R^(A) is C₁₋₄ alkyl):

These forms can be called the carbinolamine and carbinolamine ether forms of the PBD (as described in the section relating to R¹⁰ above). The balance of these equilibria depend on the conditions in which the compounds are found, as well as the nature of the moiety itself.

These particular compounds may be isolated in solid form, for example, by lyophilisation.

Isomers

Certain compounds of the invention may exist in one or more particular geometric, optical, enantiomeric, diasteriomeric, epimeric, atropic, stereoisomeric, tautomeric, conformational, or anomeric forms, including but not limited to, cis- and trans-forms; E- and Z-forms; c-, t-, and r-forms; endo- and exo-forms; R-, S-, and meso-forms; D- and L-forms; d- and l-forms; (+) and (−) forms; keto-, enol-, and enolate-forms; syn- and anti-forms; synclinal- and anticlinal-forms; α- and β-forms; axial and equatorial forms; boat-, chair-, twist-, envelope-, and halfchair-forms; and combinations thereof, hereinafter collectively referred to as “isomers” (or “isomeric forms”).

The term “chiral” refers to molecules which have the property of non-superimposability of the mirror image partner, while the term “achiral” refers to molecules which are superimposable on their mirror image partner.

The term “stereoisomers” refers to compounds which have identical chemical constitution, but differ with regard to the arrangement of the atoms or groups in space.

“Diastereomer” refers to a stereoisomer with two or more centers of chirality and whose molecules are not mirror images of one another. Diastereomers have different physical properties, e.g. melting points, boiling points, spectral properties, and reactivities. Mixtures of diastereomers may separate under high resolution analytical procedures such as electrophoresis and chromatography.

“Enantiomers” refer to two stereoisomers of a compound which are non-superimposable mirror images of one another.

Stereochemical definitions and conventions used herein generally follow S. P. Parker, Ed., McGraw-Hill Dictionary of Chemical Terms (1984) McGraw-Hill Book Company, New York; and Eliel, E. and Wilen, S., “Stereochemistry of Organic Compounds”, John Wiley & Sons, Inc., New York, 1994. The compounds of the invention may contain asymmetric or chiral centers, and therefore exist in different stereoisomeric forms. It is intended that all stereoisomeric forms of the compounds of the invention, including but not limited to, diastereomers, enantiomers and atropisomers, as well as mixtures thereof such as racemic mixtures, form part of the present invention. Many organic compounds exist in optically active forms, i.e., they have the ability to rotate the plane of plane-polarized light. In describing an optically active compound, the prefixes D and L, or R and S, are used to denote the absolute configuration of the molecule about its chiral center(s). The prefixes d and l or (+) and (−) are employed to designate the sign of rotation of plane-polarized light by the compound, with (−) or I meaning that the compound is levorotatory. A compound prefixed with (+) or d is dextrorotatory. For a given chemical structure, these stereoisomers are identical except that they are mirror images of one another. A specific stereoisomer may also be referred to as an enantiomer, and a mixture of such isomers is often called an enantiomeric mixture. A 50:50 mixture of enantiomers is referred to as a racemic mixture or a racemate, which may occur where there has been no stereoselection or stereospecificity in a chemical reaction or process. The terms “racemic mixture” and “racemate” refer to an equimolar mixture of two enantiomeric species, devoid of optical activity.

Note that, except as discussed below for tautomeric forms, specifically excluded from the term “isomers”, as used herein, are structural (or constitutional) isomers (i.e. isomers which differ in the connections between atoms rather than merely by the position of atoms in space). For example, a reference to a methoxy group, —OCH₃, is not to be construed as a reference to its structural isomer, a hydroxymethyl group, —CH₂OH. Similarly, a reference to ortho-chlorophenyl is not to be construed as a reference to its structural isomer, meta-chlorophenyl. However, a reference to a class of structures may well include structurally isomeric forms falling within that class (e.g. C₁₋₇ alkyl includes n-propyl and iso-propyl; butyl includes n-, iso-, sec-, and tert-butyl; methoxyphenyl includes ortho-, meta-, and para-methoxyphenyl).

The above exclusion does not pertain to tautomeric forms, for example, keto-, enol-, and enolate-forms, as in, for example, the following tautomeric pairs: keto/enol (illustrated below), imine/enamine, amide/imino alcohol, amidine/amidine, nitroso/oxime, thioketone/enethiol, N-nitroso/hyroxyazo, and nitro/aci-nitro.

The term “tautomer” or “tautomeric form” refers to structural isomers of different energies which are interconvertible via a low energy barrier. For example, proton tautomers (also known as prototropic tautomers) include interconversions via migration of a proton, such as keto-enol and imine-enamine isomerizations. Valence tautomers include interconversions by reorganization of some of the bonding electrons.

Note that specifically included in the term “isomer” are compounds with one or more isotopic substitutions. For example, H may be in any isotopic form, including ¹H, ²H (D), and ³H (T); C may be in any isotopic form, including ¹²C, ¹³C, and ¹⁴C; O may be in any isotopic form, including ¹⁶O and ¹⁸O; and the like.

Examples of isotopes that can be incorporated into compounds of the invention include isotopes of hydrogen, carbon, nitrogen, oxygen, phosphorous, fluorine, and chlorine, such as, but not limited to ²H (deuterium, D), ³H (tritium), ¹¹C ¹³C, ¹⁴C ¹⁵N, ¹⁸F, ³¹P, ³²P, ³⁵S, ³⁶C, and ¹²⁵I. Various isotopically labeled compounds of the present invention, for example those into which radioactive isotopes such as 3H, 13C, and 14C are incorporated. Such isotopically labelled compounds may be useful in metabolic studies, reaction kinetic studies, detection or imaging techniques, such as positron emission tomography (PET) or single-photon emission computed tomography (SPECT) including drug or substrate tissue distribution assays, or in radioactive treatment of patients. Deuterium labelled or substituted therapeutic compounds of the invention may have improved DMPK (drug metabolism and pharmacokinetics) properties, relating to distribution, metabolism, and excretion (ADME). Substitution with heavier isotopes such as deuterium may afford certain therapeutic advantages resulting from greater metabolic stability, for example increased in vivo half-life or reduced dosage requirements. An 18F labeled compound may be useful for PET or SPECT studies. Isotopically labeled compounds of this invention and prodrugs thereof can generally be prepared by carrying out the procedures disclosed in the schemes or in the examples and preparations described below by substituting a readily available isotopically labeled reagent for a non-isotopically labeled reagent. Further, substitution with heavier isotopes, particularly deuterium (i.e., 2H or D) may afford certain therapeutic advantages resulting from greater metabolic stability, for example increased in vivo half-life or reduced dosage requirements or an improvement in therapeutic index. It is understood that deuterium in this context is regarded as a substituent. The concentration of such a heavier isotope, specifically deuterium, may be defined by an isotopic enrichment factor. In the compounds of this invention any atom not specifically designated as a particular isotope is meant to represent any stable isotope of that atom.

Unless otherwise specified, a reference to a particular compound includes all such isomeric forms, including (wholly or partially) racemic and other mixtures thereof. Methods for the preparation (e.g. asymmetric synthesis) and separation (e.g. fractional crystallisation and chromatographic means) of such isomeric forms are either known in the art or are readily obtained by adapting the methods taught herein, or known methods, in a known manner.

Biological Activity In Vitro Cell Proliferation Assays

Generally, the cytotoxic or cytostatic activity of an antibody-drug conjugate (ADC) is measured by: exposing mammalian cells having receptor proteins to the antibody of the ADC in a cell culture medium; culturing the cells for a period from about 6 hours to about 5 days; and measuring cell viability. Cell-based in vitro assays are used to measure viability (proliferation), cytotoxicity, and induction of apoptosis (caspase activation) of an ADC of the invention.

The in vitro potency of antibody-drug conjugates can be measured by a cell proliferation assay. The CellTiter-Glo© Luminescent Cell Viability Assay is a commercially available (Promega Corp., Madison, Wis.), homogeneous assay method based on the recombinant expression of Coleoptera luciferase (U.S. Pat. Nos. 5,583,024; 5,674,713 and 5,700,670). This cell proliferation assay determines the number of viable cells in culture based on quantitation of the ATP present, an indicator of metabolically active cells (Crouch et al(1993) J. Immunol. Meth. 160:81-88; U.S. Pat. No. 6,602,677). The CellTiter-Glo® Assay is conducted in 96 well format, making it amenable to automated high-throughput screening (HTS) (Cree et al (1995) AntiCancer Drugs 6:398-404). The homogeneous assay procedure involves adding the single reagent (CellTiter-Glo® Reagent) directly to cells cultured in serum-supplemented medium. Cell washing, removal of medium and multiple pipetting steps are not required. The system detects as few as 15 cells/well in a 384-well format in 10 minutes after adding reagent and mixing. The cells may be treated continuously with ADC, or they may be treated and separated from ADC. Generally, cells treated briefly, i.e. 3 hours, showed the same potency effects as continuously treated cells.

The homogeneous “add-mix-measure” format results in cell lysis and generation of a luminescent signal proportional to the amount of ATP present. The amount of ATP is directly proportional to the number of cells present in culture. The CellTiter-Glo© Assay generates a “glow-type” luminescent signal, produced by the luciferase reaction, which has a half-life generally greater than five hours, depending on cell type and medium used. Viable cells are reflected in relative luminescence units (RLU). The substrate, Beetle Luciferin, is oxidatively decarboxylated by recombinant firefly luciferase with concomitant conversion of ATP to AMP and generation of photons.

The in vitro potency of antibody-drug conjugates can also be measured by a cytotoxicity assay. Cultured adherent cells are washed with PBS, detached with trypsin, diluted in complete medium, containing 10% FCS, centrifuged, re-suspended in fresh medium and counted with a haemocytometer. Suspension cultures are counted directly. Monodisperse cell suspensions suitable for counting may require agitation of the suspension by repeated aspiration to break up cell clumps.

The cell suspension is diluted to the desired seeding density and dispensed (100 μl per well) into black 96 well plates. Plates of adherent cell lines are incubated overnight to allow adherence. Suspension cell cultures can be used on the day of seeding.

A stock solution (1 ml) of ADC (20 μg/ml) is made in the appropriate cell culture medium. Serial 10-fold dilutions of stock ADC are made in 15 ml centrifuge tubes by serially transferring 100 μl to 900 μl of cell culture medium.

Four replicate wells of each ADC dilution (100 μl) are dispensed in 96-well black plates, previously plated with cell suspension (100 μl), resulting in a final volume of 200 μl. Control wells receive cell culture medium (100 μl).

If the doubling time of the cell line is greater than 30 hours, ADC incubation is for 5 days, otherwise a four day incubation is done.

At the end of the incubation period, cell viability is assessed with the Alamar blue assay. AlamarBlue (Invitrogen) is dispensed over the whole plate (20 μl per well) and incubated for 4 hours. Alamar blue fluorescence is measured at excitation 570 nm, emission 585 nm on the Varioskan flash plate reader. Percentage cell survival is calculated from the mean fluorescence in the ADC treated wells compared to the mean fluorescence in the control wells.

Use

The conjugates of the invention may be used to provide a PBD compound at a target location.

The target location is preferably a proliferative cell population. The antibody is an antibody for an antigen present on a proliferative cell population.

In one embodiment the antigen is absent or present at a reduced level in a non-proliferative cell population compared to the amount of antigen present in the proliferative cell population, for example a tumour cell population.

At the target location the linker may be cleaved so as to release a compound RelA. Thus, the conjugate may be used to selectively provide a compound RelA to the target location.

The linker may be cleaved by an enzyme present at the target location.

The target location may be in vitro, in vivo or ex vivo.

The antibody-drug conjugate (ADC) compounds of the invention include those with utility for anticancer activity. In particular, the compounds include an antibody conjugated, i.e. covalently attached by a linker, to a PBD drug moiety, i.e. toxin. When the drug is not conjugated to an antibody, the PBD drug has a cytotoxic effect. The biological activity of the PBD drug moiety is thus modulated by conjugation to an antibody. The antibody-drug conjugates (ADC) of the invention selectively deliver an effective dose of a cytotoxic agent to tumor tissue whereby greater selectivity, i.e. a lower efficacious dose, may be achieved.

Thus, in one aspect, the present invention provides a conjugate compound as described herein for use in therapy.

In a further aspect there is also provides a conjugate compound as described herein for use in the treatment of a proliferative disease. A second aspect of the present invention provides the use of a conjugate compound in the manufacture of a medicament for treating a proliferative disease.

One of ordinary skill in the art is readily able to determine whether or not a candidate conjugate treats a proliferative condition for any particular cell type. For example, assays which may conveniently be used to assess the activity offered by a particular compound are described in the examples below.

The term “proliferative disease” pertains to an unwanted or uncontrolled cellular proliferation of excessive or abnormal cells which is undesired, such as, neoplastic or hyperplastic growth, whether in vitro or in vivo.

Examples of proliferative conditions include, but are not limited to, benign, pre-malignant, and malignant cellular proliferation, including but not limited to, neoplasms and tumours (e.g. histocytoma, glioma, astrocyoma, osteoma), cancers (e.g. lung cancer, small cell lung cancer, gastrointestinal cancer, bowel cancer, colon cancer, breast carinoma, ovarian carcinoma, oesophageal cancer, prostate cancer, testicular cancer, liver cancer, kidney cancer, bladder cancer, pancreas cancer, brain cancer, sarcoma, osteosarcoma, Kaposi's sarcoma, melanoma), lymphomas, leukemias, psoriasis, bone diseases, fibroproliferative disorders (e.g. of connective tissues), and atherosclerosis. Cancers of particular interest include, but are not limited to, leukemias and ovarian cancers.

Any type of cell may be treated, including but not limited to, lung, gastrointestinal (including, e.g. bowel, colon), breast (mammary), ovarian, prostate, liver (hepatic), kidney (renal), bladder, pancreas, brain, and skin.

Disorders of particular interest include, but are not limited to cancers, including metastatic cancers and metastatic cancer cells, such as circulating tumour cells, which may be found circulating in body fluids such as blood or lymph. Cancers of particular interest include breast, lung, gastric, head and neck, colorectal, renal, pancreatic, uterine, hepatic, bladder, endometrial and prostate cancers as well as lymphomas (e.g., non-Hodgkin's lymphoma, NHL) and leukemia (particularly acute myeloid leukemia, AML).

Other disorders of interest include any condition in which Axl is overexpressed, or wherein Axl antagonism will provide a clinical benefit. These include immune disorders, cardiovascular disorders, thrombosis, diabetes, immune checkpoint disorders, fibrotic disorders (fibrosis), or proliferative diseases such as cancer, particularly metastatic cancer. Furthermore, Axl is known to play a role in many cancers of epithelial origin.

Fibrotic disorders of interest include strabmisus, scleroderma, keloid, Nephrogenic systemic fibrosis, pulmonary fibrosis, idiopathic pulmonary fibrosis (IPF), cystic fibrosis (CF), systemic sclerosis, cardiac fibrosis, non-alcoholic steatohepatitis (NASH), other types of liver fibrosis, primary biliary cirrhosis, renal fibrosis, cancer, and atherosclerosis. In these diseases, the chronic development of fibrosis in tissue leads to marked alterations in the architecture of the affected organs and subsequently cause defective organ function. As a result of this process of sustained attrition to organs, many diseases that involve fibrosis are often progressive conditions and have a poor long-term prognosis (see Rockey, D. C., Bell, P. D. and Hill, J. A. (2015), N. Engl. Med., Vol. 372, pp. 1138-1149).

It is contemplated that the antibody-drug conjugates (ADC) of the present invention may be used to treat various diseases or disorders, e.g. characterized by the overexpression of a tumor antigen. Exemplary conditions or hyperproliferative disorders include benign or malignant tumors; leukemia, haematological, and lymphoid malignancies. Others include neuronal, glial, astrocytal, hypothalamic, glandular, macrophagal, epithelial, stromal, blastocoelic, inflammatory, angiogenic and immunologic, including autoimmune, disorders.

Generally, the disease or disorder to be treated is a hyperproliferative disease such as cancer. Examples of cancer to be treated herein include, but are not limited to, carcinoma, lymphoma, blastoma, sarcoma, and leukemia or lymphoid malignancies. More particular examples of such cancers include squamous cell cancer (e.g. epithelial squamous cell cancer), lung cancer including small-cell lung cancer, non-small cell lung cancer, adenocarcinoma of the lung and squamous carcinoma of the lung, cancer of the peritoneum, hepatocellular cancer, gastric or stomach cancer including gastrointestinal cancer, pancreatic cancer, glioblastoma, cervical cancer, ovarian cancer, liver cancer, bladder cancer, hepatoma, breast cancer, colon cancer, rectal cancer, colorectal cancer, endometrial or uterine carcinoma, salivary gland carcinoma, kidney or renal cancer, prostate cancer, vulval cancer, thyroid cancer, hepatic carcinoma, anal carcinoma, penile carcinoma, as well as head and neck cancer.

Autoimmune diseases for which the ADC compounds may be used in treatment include rheumatologic disorders (such as, for example, rheumatoid arthritis, Sjögren's syndrome, scleroderma, lupus such as SLE and lupus nephritis, polymyositis/dermatomyositis, cryoglobulinemia, anti-phospholipid antibody syndrome, and psoriatic arthritis), osteoarthritis, autoimmune gastrointestinal and liver disorders (such as, for example, inflammatory bowel diseases (e.g. ulcerative colitis and Crohn's disease), autoimmune gastritis and pernicious anemia, autoimmune hepatitis, primary biliary cirrhosis, primary sclerosing cholangitis, and celiac disease), vasculitis (such as, for example, ANCA-associated vasculitis, including Churg-Strauss vasculitis, Wegener's granulomatosis, and polyarteriitis), autoimmune neurological disorders (such as, for example, multiple sclerosis, opsoclonus myoclonus syndrome, myasthenia gravis, neuromyelitis optica, Parkinson's disease, Alzheimer's disease, and autoimmune polyneuropathies), renal disorders (such as, for example, glomerulonephritis, Goodpasture's syndrome, and Berger's disease), autoimmune dermatologic disorders (such as, for example, psoriasis, urticaria, hives, pemphigus vulgaris, bullous pemphigoid, and cutaneous lupus erythematosus), hematologic disorders (such as, for example, thrombocytopenic purpura, thrombotic thrombocytopenic purpura, post-transfusion purpura, and autoimmune hemolytic anemia), atherosclerosis, uveitis, autoimmune hearing diseases (such as, for example, inner ear disease and hearing loss), Behcet's disease, Raynaud's syndrome, organ transplant, and autoimmune endocrine disorders (such as, for example, diabetic-related autoimmune diseases such as insulin-dependent diabetes mellitus (IDDM), Addison's disease, and autoimmune thyroid disease (e.g. Graves' disease and thyroiditis)). More preferred such diseases include, for example, rheumatoid arthritis, ulcerative colitis, ANCA-associated vasculitis, lupus, multiple sclerosis, Sjögren's syndrome, Graves' disease, IDDM, pernicious anemia, thyroiditis, and glomerulonephritis.

Methods of Treatment

The conjugates of the present invention may be used in a method of therapy. Also provided is a method of treatment, comprising administering to a subject in need of treatment a therapeutically-effective amount of a conjugate compound of the invention. The term “therapeutically effective amount” is an amount sufficient to show benefit to a patient. Such benefit may be at least amelioration of at least one symptom. The actual amount administered, and rate and time-course of administration, will depend on the nature and severity of what is being treated. Prescription of treatment, e.g. decisions on dosage, is within the responsibility of general practitioners and other medical doctors.

A compound of the invention may be administered alone or in combination with other treatments, either simultaneously or sequentially dependent upon the condition to be treated. Examples of treatments and therapies include, but are not limited to, chemotherapy (the administration of active agents, including, e.g. drugs, such as chemotherapeutics); surgery; and radiation therapy.

A “chemotherapeutic agent” is a chemical compound useful in the treatment of cancer, regardless of mechanism of action. Classes of chemotherapeutic agents include, but are not limited to: alkylating agents, antimetabolites, spindle poison plant alkaloids, cytotoxic/antitumor antibiotics, topoisomerase inhibitors, antibodies, photosensitizers, and kinase inhibitors. Chemotherapeutic agents include compounds used in “targeted therapy” and conventional chemotherapy.

Examples of chemotherapeutic agents include: erlotinib (TARCEVA®, Genentech/OSI Pharm.), docetaxel (TAXOTERE®, Sanofi-Aventis), 5-FU (fluorouracil, 5-fluorouracil, CAS No. 51-21-8), gemcitabine (GEMZAR, Lilly), PD-0325901 (CAS No. 391210-10-9, Pfizer), cisplatin (cis-diamine, dichloroplatinum(II), CAS No. 15663-27-1), carboplatin (CAS No. 41575-94-4), paclitaxel (TAXOL®, Bristol-Myers Squibb Oncology, Princeton, N.J.), trastuzumab (HERCEPTIN®, Genentech), temozolomide (4-methyl-5-oxo-2,3,4,6,8-pentazabicyclo [4.3.0] nona-2,7,9-triene-9-carboxamide, CAS No. 85622-93-1, TEMODAR, TEMODAL, Schering Plough), tamoxifen ((Z)-2-[4-(1,2-diphenylbut-1-enyl)phenoxy]-N,N-dimethylethanamine, NOLVADEX, ISTUBAL®, VALODEX®), and doxorubicin (ADRIAMYCIN), Akti-1/2, HPPD, and rapamycin.

More examples of chemotherapeutic agents include: oxaliplatin (ELOXATIN®, Sanofi), bortezomib (VELCADE®, Millennium Pharm.), sutent (SUNITINIB®, SU11248, Pfizer), letrozole (FEMARA®, Novartis), imatinib mesylate (GLEEVEC®, Novartis), XL-518 (Mek inhibitor, Exelixis, WO 2007/044515), ARRY-886 (Mek inhibitor, AZD6244, Array BioPharma, Astra Zeneca), SF-1126 (PI3K inhibitor, Semafore Pharmaceuticals), BEZ-235 (P3K inhibitor, Novartis), XL-147 (PI3K inhibitor, Exelixis), PTK787/ZK 222584 (Novartis), fulvestrant (FASLODEX, AstraZeneca), leucovorin (folinic acid), rapamycin (sirolimus, RAPAMUNE®, Wyeth), lapatinib (TYKERB, GSK572016, Glaxo Smith Kline), lonafarnib (SARASAR™, SCH 66336, Schering Plough), sorafenib (NEXAVAR®, BAY43-9006, Bayer Labs), gefitinib (IRESSA, AstraZeneca), irinotecan (CAMPTOSAR, CPT-11, Pfizer), tipifarnib (ZARNESTRA™, Johnson & Johnson), ABRAXANE™ (Cremophor-free), albumin-engineered nanoparticle formulations of paclitaxel (American Pharmaceutical Partners, Schaumberg, II), vandetanib (rINN, ZD6474, ZACTIMA®, AstraZeneca), chloranmbucil, AG1478, AG1571 (SU 5271; Sugen), temsirolimus (TORISEL®, Wyeth), pazopanib (GlaxoSmithKline), canfosfamide (TELCYTA, Telik), thiotepa and cyclosphosphamide (CYTOXAN®, NEOSAR); alkyl sulfonates such as busulfan, improsulfan and piposulfan; aziridines such as benzodopa, carboquone, meturedopa, and uredopa; ethylenimines and methylamelamines including altretamine, triethylenemelamine, triethylenephosphoramide, triethylenethiophosphoramide and trimethylomelamine; acetogenins (especially bullatacin and bullatacinone); a camptothecin (including the synthetic analog topotecan); bryostatin; callystatin; CC-1065 (including its adozelesin, carzelesin and bizelesin synthetic analogs); cryptophycins (particularly cryptophycin 1 and cryptophycin 8); dolastatin; duocarmycin (including the synthetic analogs, KW-2189 and CB1-TM1); eleutherobin; pancratistatin; a sarcodictyin; spongistatin; nitrogen mustards such as chlorambucil, chlornaphazine, chlorophosphamide, estramustine, ifosfamide, mechlorethamine, mechlorethamine oxide hydrochloride, melphalan, novembichin, phenesterine, prednimustine, trofosfamide, uracil mustard; nitrosoureas such as carmustine, chlorozotocin, fotemustine, lomustine, nimustine, and ranimnustine; antibiotics such as the enediyne antibiotics (e.g. calicheamicin, calicheamicin gammal1, calicheamicin omegal1 (Angew Chem. Intl. Ed. Engl. (1994) 33:183-186); dynemicin, dynemicin A; bisphosphonates, such as clodronate; an esperamicin; as well as neocarzinostatin chromophore and related chromoprotein enediyne antibiotic chromophores), aclacinomysins, actinomycin, authramycin, azaserine, bleomycins, cactinomycin, carabicin, carminomycin, carzinophilin, chromomycinis, dactinomycin, daunorubicin, detorubicin, 6-diazo-5-oxo-L-norleucine, morpholino-doxorubicin, cyanomorpholino-doxorubicin, 2-pyrrolino-doxorubicin and deoxydoxorubicin), epirubicin, esorubicin, idarubicin, nemorubicin, marcellomycin, mitomycins such as mitomycin C, mycophenolic acid, nogalamycin, olivomycins, peplomycin, porfiromycin, puromycin, quelamycin, rodorubicin, streptonigrin, streptozocin, tubercidin, ubenimex, zinostatin, zorubicin; anti-metabolites such as methotrexate and 5-fluorouracil (5-FU); folic acid analogs such as denopterin, methotrexate, pteropterin, trimetrexate; purine analogs such as fludarabine, 6-mercaptopurine, thiamiprine, thioguanine; pyrimidine analogs such as ancitabine, azacitidine, 6-azauridine, carmofur, cytarabine, dideoxyuridine, doxifluridine, enocitabine, floxuridine; androgens such as calusterone, dromostanolone propionate, epitiostanol, mepitiostane, testolactone; anti-adrenals such as aminoglutethimide, mitotane, trilostane; folic acid replenisher such as frolinic acid; aceglatone; aldophosphamide glycoside; aminolevulinic acid; eniluracil; amsacrine; bestrabucil; bisantrene; edatraxate; defofamine; demecolcine; diaziquone; elfornithine; elliptinium acetate; an epothilone; etoglucid; gallium nitrate; hydroxyurea; lentinan; lonidainine; maytansinoids such as maytansine and ansamitocins; mitoguazone; mitoxantrone; mopidanmol; nitraerine; pentostatin; phenamet; pirarubicin; losoxantrone; podophyllinic acid; 2-ethylhydrazide; procarbazine; PSK® polysaccharide complex (JHS Natural Products, Eugene, Oreg.); razoxane; rhizoxin; sizofiran; spirogermanium; tenuazonic acid; triaziquone; 2,2′,2″-trichlorotriethylamine; trichothecenes (especially T-2 toxin, verracurin A, roridin A and anguidine); urethan; vindesine; dacarbazine; mannomustine; mitobronitol; mitolactol; pipobroman; gacytosine; arabinoside (“Ara-C”); cyclophosphamide; thiotepa; 6-thioguanine; mercaptopurine; methotrexate; platinum analogs such as cisplatin and carboplatin; vinblastine; etoposide (VP-16); ifosfamide; mitoxantrone; vincristine; vinorelbine (NAVELBINE); novantrone; teniposide; edatrexate; daunomycin; aminopterin; capecitabine (XELODA®. Roche); ibandronate; CPT-11; topoisomerase inhibitor RFS 2000; difluoromethylornithine (DMFO); retinoids such as retinoic acid; and pharmaceutically acceptable salts, acids and derivatives of any of the above.

Also included in the definition of “chemotherapeutic agent” are: (i) anti-hormonal agents that act to regulate or inhibit hormone action on tumors such as anti-estrogens and selective estrogen receptor modulators (SERMs), including, for example, tamoxifen (including NOLVADEX; tamoxifen citrate), raloxifene, droloxifene, 4-hydroxytamoxifen, trioxifene, keoxifene, LY117018, onapristone, and FARESTON® (toremifine citrate); (ii) aromatase inhibitors that inhibit the enzyme aromatase, which regulates estrogen production in the adrenal glands, such as, for example, 4(5)-imidazoles, aminoglutethimide, MEGASE® (megestrol acetate), AROMASIN® (exemestane; Pfizer), formestanie, fadrozole, RIVISOR® (vorozole), FEMARA® (letrozole; Novartis), and ARIMIDEX® (anastrozole; AstraZeneca); (iii) anti-androgens such as flutamide, nilutamide, bicalutamide, leuprolide, and goserelin; as well as troxacitabine (a 1,3-dioxolane nucleoside cytosine analog); (iv) protein kinase inhibitors such as MEK inhibitors (WO 2007/044515); (v) lipid kinase inhibitors; (vi) antisense oligonucleotides, particularly those which inhibit expression of genes in signaling pathways implicated in aberrant cell proliferation, for example, PKC-alpha, Raf and H-Ras, such as oblimersen (GENASENSE®, Genta Inc.); (vii) ribozymes such as VEGF expression inhibitors (e.g., ANGIOZYME) and HER2 expression inhibitors; (viii) vaccines such as gene therapy vaccines, for example, ALLOVECTIN®, LEUVECTIN®, and VAXID®; PROLEUKIN® rlL-2; topoisomerase 1 inhibitors such as LURTOTECAN®; ABARELIX® rmRH; (ix) anti-angiogenic agents such as bevacizumab (AVASTIN®, Genentech); and pharmaceutically acceptable salts, acids and derivatives of any of the above.

Also included in the definition of “chemotherapeutic agent” are therapeutic antibodies such as alemtuzumab (Campath), bevacizumab (AVASTIN®, Genentech); cetuximab (ERBITUX, Imclone); panitumumab (VECTIBIX®, Amgen), rituximab (RITUXAN®, Genentech/Biogen Idec), ofatumumab (ARZERRA, GSK), pertuzumab (PERJETA™ OMNITARG™, 2C4, Genentech), trastuzumab (HERCEPTIN®, Genentech), tositumomab (Bexxar, Corixia), and the antibody drug conjugate, gemtuzumab ozogamicin (MYLOTARG®, Wyeth).

Humanized monoclonal antibodies with therapeutic potential as chemotherapeutic agents in combination with the conjugates of the invention include: alemtuzumab, apolizumab, aselizumab, atlizumab, bapineuzumab, bevacizumab, bivatuzumab mertansine, cantuzumab mertansine, cedelizumab, certolizumab pegol, cidfusituzumab, cidtuzumab, daclizumab, eculizumab, efalizumab, epratuzumab, erlizumab, felvizumab, fontolizumab, gemtuzumab ozogamicin, inotuzumab ozogamicin, ipilimumab, labetuzumab, lintuzumab, matuzumab, mepolizumab, motavizumab, motovizumab, natalizumab, nimotuzumab, nolovizumab, numavizumab, ocrelizumab, omalizumab, palivizumab, pascolizumab, pecfusituzumab, pectuzumab, pertuzumab, pexelizumab, ralivizumab, ranibizumab, reslivizumab, reslizumab, resyvizumab, rovelizumab, ruplizumab, sibrotuzumab, siplizumab, sontuzumab, tacatuzumab tetraxetan, tadocizumab, talizumab, tefibazumab, tocilizumab, toralizumab, trastuzumab, tucotuzumab celmoleukin, tucusituzumab, umavizumab, urtoxazumab, and visilizumab.

Pharmaceutical compositions according to the present invention, and for use in accordance with the present invention, may comprise, in addition to the active ingredient, i.e. a conjugate compound, a pharmaceutically acceptable excipient, carrier, buffer, stabiliser or other materials well known to those skilled in the art. Such materials should be non-toxic and should not interfere with the efficacy of the active ingredient. The precise nature of the carrier or other material will depend on the route of administration, which may be oral, or by injection, e.g. cutaneous, subcutaneous, or intravenous.

Pharmaceutical compositions for oral administration may be in tablet, capsule, powder or liquid form. A tablet may comprise a solid carrier or an adjuvant. Liquid pharmaceutical compositions generally comprise a liquid carrier such as water, petroleum, animal or vegetable oils, mineral oil or synthetic oil. Physiological saline solution, dextrose or other saccharide solution or glycols such as ethylene glycol, propylene glycol or polyethylene glycol may be included. A capsule may comprise a solid carrier such a gelatin.

For intravenous, cutaneous or subcutaneous injection, or injection at the site of affliction, the active ingredient will be in the form of a parenterally acceptable aqueous solution which is pyrogen-free and has suitable pH, isotonicity and stability. Those of relevant skill in the art are well able to prepare suitable solutions using, for example, isotonic vehicles such as Sodium Chloride Injection, Ringer's Injection, Lactated Ringer's Injection. Preservatives, stabilisers, buffers, antioxidants and/or other additives may be included, as required.

Formulations

While it is possible for the conjugate compound to be used (e.g., administered) alone, it is often preferable to present it as a composition or formulation.

In one embodiment, the composition is a pharmaceutical composition (e.g., formulation, preparation, medicament) comprising a conjugate compound, as described herein, and a pharmaceutically acceptable carrier, diluent, or excipient.

In one embodiment, the composition is a pharmaceutical composition comprising at least one conjugate compound, as described herein, together with one or more other pharmaceutically acceptable ingredients well known to those skilled in the art, including, but not limited to, pharmaceutically acceptable carriers, diluents, excipients, adjuvants, fillers, buffers, preservatives, anti-oxidants, lubricants, stabilisers, solubilisers, surfactants (e.g., wetting agents), masking agents, colouring agents, flavouring agents, and sweetening agents.

In one embodiment, the composition further comprises other active agents, for example, other therapeutic or prophylactic agents.

Suitable carriers, diluents, excipients, etc. can be found in standard pharmaceutical texts. See, for example, Handbook of Pharmaceutical Additives, 2nd Edition (eds. M. Ash and I. Ash), 2001 (Synapse Information Resources, Inc., Endicott, New York, USA), Remington's Pharmaceutical Sciences, 20th edition, pub. Lippincott, Williams & Wilkins, 2000; and Handbook of Pharmaceutical Excipients, 2nd edition, 1994.

Another aspect of the present invention pertains to methods of making a pharmaceutical composition comprising admixing at least one [¹¹C]-radiolabelled conjugate or conjugate-like compound, as defined herein, together with one or more other pharmaceutically acceptable ingredients well known to those skilled in the art, e.g., carriers, diluents, excipients, etc. If formulated as discrete units (e.g., tablets, etc.), each unit contains a predetermined amount (dosage) of the active compound.

The term “pharmaceutically acceptable,” as used herein, pertains to compounds, ingredients, materials, compositions, dosage forms, etc., which are, within the scope of sound medical judgment, suitable for use in contact with the tissues of the subject in question (e.g., human) without excessive toxicity, irritation, allergic response, or other problem or complication, commensurate with a reasonable benefit/risk ratio. Each carrier, diluent, excipient, etc. must also be “acceptable” in the sense of being compatible with the other ingredients of the formulation.

The formulations may be prepared by any methods well known in the art of pharmacy. Such methods include the step of bringing into association the active compound with a carrier which constitutes one or more accessory ingredients. In general, the formulations are prepared by uniformly and intimately bringing into association the active compound with carriers (e.g., liquid carriers, finely divided solid carrier, etc.), and then shaping the product, if necessary.

The formulation may be prepared to provide for rapid or slow release; immediate, delayed, timed, or sustained release; or a combination thereof.

Formulations suitable for parenteral administration (e.g., by injection), include aqueous or non-aqueous, isotonic, pyrogen-free, sterile liquids (e.g., solutions, suspensions), in which the active ingredient is dissolved, suspended, or otherwise provided (e.g., in a liposome or other microparticulate). Such liquids may additional contain other pharmaceutically acceptable ingredients, such as anti-oxidants, buffers, preservatives, stabilisers, bacteriostats, suspending agents, thickening agents, and solutes which render the formulation isotonic with the blood (or other relevant bodily fluid) of the intended recipient. Examples of excipients include, for example, water, alcohols, polyols, glycerol, vegetable oils, and the like. Examples of suitable isotonic carriers for use in such formulations include Sodium Chloride Injection, Ringer's Solution, or Lactated Ringer's Injection. Typically, the concentration of the active ingredient in the liquid is from about 1 ng/ml to about 10 μg/ml, for example from about 10 ng/ml to about 1 μg/ml. The formulations may be presented in unit-dose or multi-dose sealed containers, for example, ampoules and vials, and may be stored in a freeze-dried (lyophilised) condition requiring only the addition of the sterile liquid carrier, for example water for injections, immediately prior to use. Extemporaneous injection solutions and suspensions may be prepared from sterile powders, granules, and tablets.

Dosage

It will be appreciated by one of skill in the art that appropriate dosages of the conjugate compound, and compositions comprising the conjugate compound, can vary from patient to patient. Determining the optimal dosage will generally involve the balancing of the level of therapeutic benefit against any risk or deleterious side effects. The selected dosage level will depend on a variety of factors including, but not limited to, the activity of the particular compound, the route of administration, the time of administration, the rate of excretion of the compound, the duration of the treatment, other drugs, compounds, and/or materials used in combination, the severity of the condition, and the species, sex, age, weight, condition, general health, and prior medical history of the patient. The amount of compound and route of administration will ultimately be at the discretion of the physician, veterinarian, or clinician, although generally the dosage will be selected to achieve local concentrations at the site of action which achieve the desired effect without causing substantial harmful or deleterious side-effects.

Administration can be effected in one dose, continuously or intermittently (e.g., in divided doses at appropriate intervals) throughout the course of treatment. Methods of determining the most effective means and dosage of administration are well known to those of skill in the art and will vary with the formulation used for therapy, the purpose of the therapy, the target cell(s) being treated, and the subject being treated. Single or multiple administrations can be carried out with the dose level and pattern being selected by the treating physician, veterinarian, or clinician.

In general, a suitable dose of the active compound is in the range of about 100 ng to about 25 mg (more typically about 1 μg to about 10 mg) per kilogram body weight of the subject per day. Where the active compound is a salt, an ester, an amide, a prodrug, or the like, the amount administered is calculated on the basis of the parent compound and so the actual weight to be used is increased proportionately.

In one embodiment, the active compound is administered to a human patient according to the following dosage regime: about 100 mg, 3 times daily.

In one embodiment, the active compound is administered to a human patient according to the following dosage regime: about 150 mg, 2 times daily.

In one embodiment, the active compound is administered to a human patient according to the following dosage regime: about 200 mg, 2 times daily.

However in one embodiment, the conjugate compound is administered to a human patient according to the following dosage regime: about 50 or about 75 mg, 3 or 4 times daily.

In one embodiment, the conjugate compound is administered to a human patient according to the following dosage regime: about 100 or about 125 mg, 2 times daily.

The dosage amounts described above may apply to the conjugate (including the PBD moiety and the linker to the antibody) or to the effective amount of PBD compound provided, for example the amount of compound that is releasable after cleavage of the linker.

For the prevention or treatment of disease, the appropriate dosage of an ADC of the invention will depend on the type of disease to be treated, as defined above, the severity and course of the disease, whether the molecule is administered for preventive or therapeutic purposes, previous therapy, the patient's clinical history and response to the antibody, and the discretion of the attending physician. The molecule is suitably administered to the patient at one time or over a series of treatments. Depending on the type and severity of the disease, about 1 μg/kg to 15 mg/kg (e.g. 0.1-20 mg/kg) of molecule is an initial candidate dosage for administration to the patient, whether, for example, by one or more separate administrations, or by continuous infusion. A typical daily dosage might range from about 1 μg/kg to 100 mg/kg or more, depending on the factors mentioned above. An exemplary dosage of ADC to be administered to a patient is in the range of about 0.1 to about 10 mg/kg of patient weight. For repeated administrations over several days or longer, depending on the condition, the treatment is sustained until a desired suppression of disease symptoms occurs. An exemplary dosing regimen comprises a course of administering an initial loading dose of about 4 mg/kg, followed by additional doses every week, two weeks, or three weeks of an ADC. Other dosage regimens may be useful. The progress of this therapy is easily monitored by conventional techniques and assays.

Treatment

The term “treatment,” as used herein in the context of treating a condition, pertains generally to treatment and therapy, whether of a human or an animal (e.g., in veterinary applications), in which some desired therapeutic effect is achieved, for example, the inhibition of the progress of the condition, and includes a reduction in the rate of progress, a halt in the rate of progress, regression of the condition, amelioration of the condition, and cure of the condition. Treatment as a prophylactic measure (i.e., prophylaxis, prevention) is also included.

The term “therapeutically-effective amount,” as used herein, pertains to that amount of an active compound, or a material, composition or dosage from comprising an active compound, which is effective for producing some desired therapeutic effect, commensurate with a reasonable benefit/risk ratio, when administered in accordance with a desired treatment regimen.

Similarly, the term “prophylactically-effective amount,” as used herein, pertains to that amount of an active compound, or a material, composition or dosage from comprising an active compound, which is effective for producing some desired prophylactic effect, commensurate with a reasonable benefit/risk ratio, when administered in accordance with a desired treatment regimen.

Preparation of Drug conjugates

The antibody drug conjugates of the present invention may be prepared by conjugating the following drug linker:

to the azide-containing antibody by the methods as described in for example, van Geel, R., et al., Bioconjugate Chemistry, 2015, 26, 2233-2242; DOI: 10.1021/acs.bioconjchem.5b00224. Suitable methods include, but are not limited to, copper-free conjugation, in for example, aqueous conditions with an optional cosolvent selected from DMF, DMSO and DMA.

The drug linker may be synthesised in accordance with the examples, with appropriate modifications, for example, referring to WO 2016/053107 for synthesis of the linker and the following documents for the PBD dimer, for example: WO 2011/130598, WO2013/055987, WO2014/057074.

The Subject/Patient

The subject/patient may be an animal, mammal, a placental mammal, a marsupial (e.g., kangaroo, wombat), a monotreme (e.g., duckbilled platypus), a rodent (e.g., a guinea pig, a hamster, a rat, a mouse), murine (e.g., a mouse), a lagomorph (e.g., a rabbit), avian (e.g., a bird), canine (e.g., a dog), feline (e.g., a cat), equine (e.g., a horse), porcine (e.g., a pig), ovine (e.g., a sheep), bovine (e.g., a cow), a primate, simian (e.g., a monkey or ape), a monkey (e.g., marmoset, baboon), an ape (e.g., gorilla, chimpanzee, orangutang, gibbon), or a human.

Furthermore, the subject/patient may be any of its forms of development, for example, a foetus. In one preferred embodiment, the subject/patient is a human.

Examples Synthesis of Intermediate 3

A solution of BCN alcohol (0.384 g, 2.55 mmole) in MeCN (25 mL) under a N₂ atmosphere was cooled to 0° C., and chlorosulfonyl isocyanate was added (CSI) was added dropwise (0.255 mL, 415 mg, 2.93 mmole, 1.15 equiv.). After stirring for 15 minutes, Et₃N was added dropwise (1.42 mL, 1.03 g, 10.2 mmole, 4 equiv.) and stirring was continued for another 10 minutes. Next, a solution of 2-(2-(2-aminoethoxy)ethoxy)acetic acid (1.0 g, 6.1 mmole, 2.4 equiv.) in H₂O (5 mL) was added and the reaction mixture was stirred to room temperature for 2 h. After this time, CHCl₃ (50 mL) and H₂O (100 mL) were added, and the layers were separated. To the aqueous layer in a separatory funnel was added CH₂Cl₂ (100 mL) and the pH was adjusted to 4 with 1 N HCl, before separation of layers. The water layer was extracted twice with CH₂Cl₂ (2×100 mL), the organic layers were combined and dried (Na₂SO₄), filtered and concentrated. The residue was purified by flask column chromatography on silica, elution with CH₂Cl₂ to 20% MeOH in CH₂Cl₂. Yield 0.42 g (1.0 mmole, 39%) of 3 as a colorless sticky wax.

Synthesis of Drug Linker

Compound 1 can be synthesised as described in WO2014/057074—see compound 22.

(a) Palladium tetrakistriphenylphosphine (Pd(PPh₃)₄, 4.8 mg, 4.15 μmol) is weighed and put under an inert atmosphere. A solution of pyrrolidine (5.0 μL, 4.3 mg, 60 μmol) in DCM (1 mL) is degassed by bubbling N₂ through the solution. A solution of 1 (27 mg, 24 μmol) in DCM (6 mL) is degassed by bubbling N₂ through the solution. While N₂ is still bubbled through the solution, the degassed solution of pyrrolidine is added. The weighed Pd(PPh₃)₄ is dissolved in DCM (1 mL) and 0.9 mL of this solution is added. After 50 min of bubbling of N₂, DCM (25 mL) is added and the mixture is washed with aqueous saturated NH₄C (25 mL). After separation, the aqueous layer is extracted with DCM (2×25 mL). The combined organic layers are dried (Na₂SO₄) and concentrated. The residue is purified by RP-HPLC (30-90% MeCN (0.1% formic acid) in H₂O (0.1% formic acid). The combined fractions are passed through SPE (HCO₃) columns and concentrated. After addition of MeCN (50 mL) the mixture is again concentrated. The resulting residue 2 is used in the next step.

The conversion of the reaction can be monitored through LCMS analysis. Column: XBridge BEH C18 Intelligent Speed (IS) Column, 130 Å, 3.5 μm (4.6 mm×20 mm). Mobile phase A: Water (0.1% formic acid), Mobile phase B (0.1% formic acid). Detection with PDA and ESI+. Samples can be prepared by diluting the reaction mixture with MeCN.

(b) To a solution of the above residue 2 in CHCl₃ (5 mL) is added a solution of 3 (15 mg, 36 μmol, mw 418 g/mole) in CHCl₃ (0.8 mL). The resulting mixture is added to solid EDC.HCl (4.7 mg, 25 μmol), CHCl₃ (5 mL) was added and the mixture stirred for 30 minutes. DCM (30 mL) is added and the resulting mixture is washed with water (30 mL). After separation, the aqueous phase is extracted with DCM (30 mL). The combined organic layers are dried (Na₂SO₄) and concentrated. The residue is purified by RP-HPLC (30-90% MeCN (no acid) in H₂O (0.01% formic acid). The HPLC collection tubes are filled with 5% aqueous (NH₄)HCO₃ before collection. The combined HPLC fractions are extracted with DCM (3×20 mL). The combined organic layers are dried (Na₂SO₄) and concentrated. The product 4 is obtained as slightly yellow/white oil (21 mg, 16 μmol, mw 1323 g/mole, 67% over two steps).

The conversion of the reaction can be monitored through LCMS analysis. Column: XBridge BEH C18 Intelligent Speed (IS) Column, 130 Å, 3.5 μm (4.6 mm×20 mm). Mobile phase A: Water (0.1% formic acid), Mobile phase B (0.1% formic acid). Detection with PDA and ESI+.

Antibody Modification Reaction Conditions

The reaction conditions for the one-pot glycan remodelling are:

-   -   15 mg/ml Antibody (˜0.1 mM)     -   0.15 mg/mL EndoSH (1% w/w) from Streptococcus pyogenes     -   1.13 mg/mL His-TnGalNAcT (7.5% w/w) Galactose-N-acetyl         Transferase (GalNAcT)     -   enzyme     -   2.5 mM 6-N₃GalNAc-UDP (25 eq. compared to IgG)     -   10 mM MnCl₂     -   25 mM TrisHCI ph 8.0     -   150 mM NaCl     -   Incubate 16 hours at 30° C.

This was carried out on AXL and B12.

Procedure

This example is on a 25 mg-scale, which may be altered as necessary. The individual components are added in order and mixed:

-   -   106.5 μL 25 mM Tris pH 8.0, 150 mM NaCl (to obtain a final         volume of 1667 μL)     -   1 mL 25 mg/mL Antibody in 25 mM Tris pH 8.0, 150 mM NaCl     -   71.4 μL 3.5 mg/mL EndoSH in 25 mM Tris pH 8.0     -   389 μL 4.82 mg/mL His-TnGalNAcT in 25 mM Tris pH 8.0     -   16.7 μL 1M MnCl₂ in MQ     -   83.4 μL 0.1 M 6-N₃GalNAc-UDP in MQ

This mixture for approximately 16 hours at 30° C. Completion of the modified galactose residue may be assessed by subjecting a sample to MS analysis. After protein A affinity purification, a small sample of the product may be reduced with DTT and subsequently subjected to MS analysis. A typical mass spectrum of a successful transfer reaction shows the formation of a one major product of (90% of total heavy chain), resulting from modified galactose transfer to core GlcNAc(Fuc) substituted Ab, and a minor product (±10% of total heavy chain), resulting from modified galactose transfer to core GlcNAc (without Fucose) substituted Ab.

Purification Procedure Buffers

Binding/wash buffer (TBS pH 7.5):

-   -   20 mM TrisHCI ph 7.5     -   150 mM NaCl         Wash buffer for endotoxin removal (TBS pH 7.5+Triton-X100):     -   20 mM TrisHCI pH 7.5     -   150 mM NaCl     -   0.2% Triton X-100         Elution buffer:     -   0.1 M Glycine pH 2.7         CIP buffer:     -   0.5 M NaOH

Procedure

1. Wash the MabSelectSure 5 mL colum (5 mL/min) with the following buffers in order to clean the column before applying the sample:

-   -   Wash column with at least 5 column volumes (CV) TBS pH 7.5     -   Wash column with 15 CV 0.5 M NaOH     -   Wash column with 5 CV TBS pH 7.5     -   Wash column with 5 CV Glycine pH 2.7     -   Wash column with TBS pH 7.5 until a natural pH is obtained         2. Remove precipitation from reaction mixture by centrifugation         (5 min at 4000 g) or by filtration (0.22 or 0.45 μm filter)         3. Load sample at 2 mL/min and perform the following steps with         5 mL/min:     -   Wash with at least 20 CV TBS=0.2% Triton X-100     -   Wash with at least 20 CV TBS     -   Elute with 0.1 M Glycine ph 2.7         4. Immediately neutralize fractions by adding 1/5 volume of 1 M         Tric-HCl ph 8.0 and mixing         5. Dialyze sample against 3×≥50 volumes of PBS pH 7.4 at 4° C.         (3×≥1 hour)         6. Concentrate sample using spinfilter devices to −20 mg/mL         Conjugation of 4 to modified antibody to produce ConjA and ConB

Reaction Conditions

-   -   15 mg/ml azido-modified antibody (0.1 M IgG)     -   0.5 mM 4 (5 eq. compared to IgG=2.5 eq per azide)     -   10% DMF or 25% propylenegycol     -   PBS pH7.4

Procedure

1. Add 9 vols of 16.67 mg/ml azido-modified antibody in PBS pH7 2. Add 1 vol of 5 mM 4 in DMF and mix immediately. 3. Incubate overnight. 4. Measure conversion by RP-HPLC and MS.

Conjugate Antibody ConjA AXL ConjB B12

Purification of ADC Sample Preparation

The following requirements should be met before loading onto the column:

-   -   Organic solvent 55%     -   Total sample volume 53% of the CV (5720 μL for Superdex 200         10/300 GL, and 510 ml for Superdex 200 HiLoad 26/600)     -   No precipitants

The above requirements can be accomplished using the following procedure:

1. Dilute sample with PBS pH7.4 to a final organic solvent concentration of 55% 2. If volume exceeds 3% of the CV, the sample was concentrated using Amicon Ultra centrifugal filters (MWCO 10 kDa) 3. Potential precipitation is removed by centrifugation (10 min at 13000 rpm in a table top centrifuge)

Purification

The purification was carried out using a Superdex 200 10/300 GL column (CV=23 ml, GE healthcare) on an Akta Purifier-10. The following washing steps are performed with a flow rate of 0.5 ml/min:

-   -   Wash column with 1 CV water     -   Wash column with 1 CV 0.5 M NaOH.     -   Equilibrate column with PBS pH 7.4 (Sigma, D8537) until neutral         pH is obtained.

The sample is injected with 0.5 ml/min PBS pH7.4 and 1 ml fractions are collected (total run=1.5 CV). Monomer fractions are pooled and dialysed at 4° C. against 3×1L of formulation buffer (30 mM histidine, 200 mM sorbitol, 0.02% (w/v) tween-20, pH 6.0). Samples are filter-sterilized using 0.22 μm filter, snapfrozen using liquid nitrogen and stored at −80° C.

Mass spectral analysis of the fabricator-digested sample showed one major product (observed mass 25691 Da, approximately 90% of total Fc/2 fragment), corresponding to the conjugated Fc/2 fragment. RP-HPLC analysis of the reduced sample indicated an average DAR of 1.98.

In Vitro Cytotoxicity

H1299 cells were obtained from ATCC (ATCC number CRL-5803). H1299 medium was Dulbecco's Modified Eagle Medium (DMEM) supplemented with 10% Gibco FBS. Cells were grown at 37° C., 5% CO₂ in a humidified incubator. Cell suspensions were dispensed into 96-well flat bottomed plates (104 cells per well). A set of 8×10-fold dilutions of stock ADC were prepared in cell culture medium. Each ADC dilution (50 μl per well) was dispensed into 4 replicate wells of the 96-well plate containing cell suspension. Control wells were prepared by adding the same volume of culture medium only. After incubation for 96 hours, cell viability was measured by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxy-phenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay (Promega, catalogue number G5421) following manufacturer's instructions. Absorbance was measured at 490 nm. Cell survival (%) was calculated from the mean absorbance in the 4 ADC-treated wells compared to the mean absorbance in the 4 control wells (100%). Dose response curves were generated from the mean data of 3 replicate experiments and the EC₅₀ values were determined by fitting data to a sigmoidal dose-response curve with variable slope using Prism (GraphPad, San Diego, Calif.). Error bars indicate standard deviation (SD).

The EC₅₀ of ConjA was found to be 0.0554 μg/mL.

Antigen Binding Study

Maxisorp plates were coated at +4° C. overnight with human Axl antigen (50 ng/well; batch in PBS. Non-reactive sites were blocked with SuperBlock buffer (overnight at +4° C. or room temperature). A set of 8×3-fold or 5-fold dilutions of stock ADC were prepared in sample buffer/PBS/Tween20. Each ADC dilution (60 μL/well) was dispensed into 4 replicate wells of the coated plate. Control wells were prepared by adding the same volume of sample buffer/PBS/Tween20. Anti-human kappa IgG-horseradish peroxidase (HRP) conjugate was used as secondary antibody (1:5000, 1 hour at room temperature). HRP was detected with 1-Step Ultra TMB-ELISA substrate solution (75 μL/well; 5 minutes at room temperature). Substrate reaction was stopped with 0.6 M HCl (75 μL/well). Optical density was measured at 450 nm on Envision using 450 nm Peroxidase program. Antigen binding curves were generated from the mean data of 3 replicate experiments using Prism (GraphPad, San Diego, Calif.). FIG. 1 shows the results obtained, where A is ConjA. Error bars indicate standard error of the mean (SEM). ConjA bound with high affinity to the extracellular domain of AXL coated on plates.

In Vivo Efficacy Study—MDA-MB-231

5×10⁶ MDA-MB-231 tumor cells were subcutaneously implanted to female athymic nude mice. ADC dosing with vehicle or test item was initiated when tumor volumes reached 88-172 mm³. ConjA was administrated intravenously (i.v.) via tail vein injection once at a dose level of 1 mg/kg. The dosing volume was 10 mL/kg of body weight and was escalated to the body weight of each individual animal. Animals were euthanized if their tumor volume reached the endpoint volume of 1500 mm³ or at the end of the study, whichever came first. Animals weight, signs of any adverse, treatment-related side effects and clinical signs were monitored during the study period. For the calculation of mean tumour volume of the group, the following rule was applied: when an animal exited the study due to tumour size, the final tumour volume recorded for the animal was included with the data used to calculate the mean volume at subsequent time points. Tumour volume and body weight values were not used to calculate a group mean tumour volumes/body weight when fewer than 50% of the animals in a group remained in the study. Prism (GraphPad, San Diego, Calif.) was used for graphical presentations and statistical analyses. FIG. 2 shows the results obtained, where ▴ is ConjA, and ◯ is the vehicle alone. Error bars indicate SEM.

A single dose of 1 mg/kg of ConjA strongly inhibited tumor growth with 10/10 mice being tumor-free 60 days after dosing.

Rat Toxicology Study Method

ConjA was evaluated in a single intravenous dose rat tolerability study. Male sprague-dawley rats (n=3/group) were dosed 3 & 6 mg/kg for ConjA on day 1, with necropsy on day 21 following dosing. Bodyweights and food consumption were monitored frequently with in-life sampling for clinical pathology (blood on days 8 and 21) and repeated sampling for pharmacokinetics. At necropsy, macroscopic observations were taken with selected organs weighed and retained for possible histopathology.

ConjA was clinically well tolerated at 3 & 6 mg/kg. Bodyweight gain was reduced by 11 and 21% in the 3 and 6 mg/kg groups respectively, consistent with reduced food consumption. Several haematology parameters were reduced on day 8, mainly in the 6 mg/kg dose group (reticulocytes (−76%), haemoglobin (−29%) white blood cells (−66%) and platelets (−37%)), with some evidence of recovery by day 21. At necropsy, reduced thymus weight was observed in all animals. Therefore, the maximum tolerated dose (MTD) for ConjA was 6 mg/kg.

In Vivo Efficacy Study—SN12C

Female severe combined immunodeficient mice (Fox Chase SCID®, CB17/lcr-Prkdcscid/lcrlcoCrl, Charles River) were ten weeks old with a body weight (BW) range of 18.0 to 21.6 g on Day 1 of the study. On the day of tumor implant, each test mouse received 5×10⁶ SN12C cells (0.1 mL cell suspension in 50% Matrigel® Matrix (Corning®) in phosphate buffered saline) implanted subcutaneously in the right flank. SN12C is a human renal cell carcinoma-derived xenograft model with high level of AXL expression (˜88,000 copies per cell).

Tumor growth was monitored as the average size approached the target range of 100 to 150 mm³. Tumors were measured in two dimensions using calipers, and volume was calculated using the formula:

Tumor Volume (mm³)=w ² ×l/2

where w=width and l=length, in mm, of the tumor. Tumor weight may be estimated with the assumption that 1 mg is equivalent to 1 mm³ of tumor volume.

Twenty-five days after tumor implantation, designated as Day 1 of the study, the animals were sorted into five groups (n=8) with individual tumor volumes of 108 to 172 mm³ and group mean tumor volumes of 120 to 123 mm³. All treatments were administered i.v. in the lateral tail vein in a single injection on Day 1 of the study. The dosing volume was 0.2 mL per grams of body weight (10 mL/kg), and was scaled to the body weight of each individual animal. Tumors were measured using calipers twice per week, and each animal was euthanized when its tumor reached the endpoint volume of 2000 mm³ or at the end of the study, whichever came first. The study ended on Day 60. At a dose of 1 mg/kg, ConjA resulted in 7/8 complete respondera (CR) and 6/8 tumor free survivors (TFS) at the end of the study on day 60.

FIG. 3 shows the results obtained, where:

◯ is the vehicle alone; ⋄ is ConjB dosed at 1 mg/kg; □ is ConjA dosed at 0.3 mg/kg; Δ is ConjA dosed at 0.6 mg/kg; ∇ is ConjA dosed at 1 mg/kg. Error bars indicate SEM.

In Vivo Efficacy Study—Karpas299 (AXL-Negative)

Female severe combined immunodeficient mice (Fox Chase SCID®, CB17/lcr-Prkdcscid/lcrlcoCrl, Charles River) were nine weeks old with a body weight (BW) range of 17.0 to 22.5 g on Day 1 of the study. On the day of tumor implant, each test mouse received 1×10⁷ Karpas-299 cells (0.1 mL cell suspension in PBS) implanted subcutaneously in the right flank.

Tumor growth was monitored as the average size approached the target range of 100 to 150 mm³. Tumors were measured in two dimensions using calipers, and volume was calculated using the formula:

Tumor Volume (mm³)=w ² ×l/2

where w=width and l=length, in mm, of the tumor. Tumor weight may be estimated with the assumption that 1 mg is equivalent to 1 mm³ of tumor volume.

Ten days after tumor implantation, designated as Day 1 of the study, the animals were sorted into four groups with individual tumor volumes of 108 to 126 mm³ and group mean tumor volumes of 113 to 117 mm³. All treatments were administered i.v. in the lateral tail vein in a single injection on Day 1 of the study. The dosing volume was 0.2 mL per 20 grams of body weight (10 mL/kg), and was scaled to the body weight of each individual animal. Tumors were measured using calipers twice per week, and each animal was euthanized when its tumor reached the endpoint volume of 2000 mm³ or at the end of the study, whichever came first. The study ended on Day 29.

FIG. 4 shows the results obtained, where:

◯ is the vehicle alone; □ is ConjA dosed at 1 mg/kg. Error bars indicate SEM.

In Vivo Efficacy Study—Pancreatic Cancer Patient-Derived Xenograft (PDX) PAXF 1657 Model

Female nu/nu mice (NU-Foxn1nu) from Charles River were at least 8 weeks old with a body weight (BW) range of 22.0 to 30.0 g on Day 0. On the day of implant, tumor fragments were obtained from xenografts in nude mice. After removal from donor mice, tumors were cut into fragments (3-4 mm edge length) and placed in PBS containing 10% penicillin/streptomycin. Recipient animals were anesthetized by inhalation of isoflurane and received unilateral or bilateral tumor implants subcutaneously in the flank.

Animals and tumor implants were monitored as their implant volumes approached the target range of 50 to 250 mm³ in a sufficient number of animals. Tumors were measured in two dimensions using calipers, and volume was calculated using the formula:

Tumor Volume (mm³)=w ² ×l/2

where w=width and l=length, in mm, of the tumor.

The day of randomization was designated as Day 0 of the experiment. On Day 1 of the experiment, female nu/nu mice bearing subcutaneous PAXF 1657 xenografts (group mean tumor volumes 109.0-110.1 mm³) were sorted into groups (n=8 per group) and dosing was initiated. The dosing volume was 0.1 ml per 20 grams of body weight (5 ml/kg), and was scaled to the body weight of each individual animal. All treatments were administered intravenously (i.v.) in a single injection on Day 1 (qd×1). Tumors were measured using calipers twice per week, and each animal was euthanized when its tumor reached the endpoint volume of 2000 mm³ or at the end of the study, whichever came first. The study ended on Day 42. Each single dose of ConjA (0.3, 0.6 and 1 mg/kg) resulted in complete eradication of the tumors at the end of the study.

FIG. 5 shows the results obtained, where:

◯ is the vehicle alone; ⋄ is ConjB dosed at 1 mg/kg; □ is ConjA dosed at 0.3 mg/kg; Δ is ConjA dosed at 0.6 mg/kg; ∇ is ConjA dosed at 1 mg/kg. Error bars indicate SEM. The vertical dotted line indicates the start of dosing (day 1).

In Vivo Efficacy Study—Oesophageal Cancer Patient-Derived Xenograft (PDX) ES0195 Model

Female Balb/c nude mice from Beijing AniKeeper Bio-Technology Co. Ltd. were 5-6 weeks old with a body weight range of 20.2-24.6 g at study initiation. Tumour fragments (2-3 mm in diameter, in ice cold RPM11640 media without serum) were inoculated subcutaneously into the right flank of 24 female Balb/c nude mice.

All animals were randomly allocated to the 3 different study groups. Randomization was performed using the multi-task method in the Study Log software on day 0. Average tumor volume (mm³) for each group+SD at randomization was as follows, ˜141 mm³±47 mm³.

All treatments were administered intravenously (i.v.) in a single injection on Day 1 (qd×1). Body weights were measured twice weekly for the duration of the study. Tumour volumes were measured twice weekly. The study was terminated on day 51 post initiation of dosing.

FIG. 6 shows the results obtained, where:

◯ is the vehicle alone; □ is ConjA dosed at 1 mg/kg; Δ is ConjB dosed at 1 mg/kg; Error bars indicate SEM. The vertical dotted line indicates the start of dosing (day 1).

In Vitro Bystander Activity Study

The in vitro cytotoxicity of ConjA and an isotype control ADC, ConjB, was compared in SN12C and Karpas-299 cell lines—Karpas299 are AXL-negative. SN12C are AXL-positive. Adherent SN12C cells were trypsined, re-suspended in 1 ml growth medium and mixed gently before counting to determine the cell density. Suspension Karpas299 cells were counted without any pre-treatment. Cell density was determined in duplicate by Trypan blue exclusion assay using a LUNA-II™ automated cell counter. SN12C cell suspension was diluted to 1×10⁴ cells/ml in cell specific growth media and 100 μl/well was dispensed into sterile white 96-well flat-bottomed microplates and incubated overnight to allow cells to adhere. Karpas299 cells were seeded on the same day as ADC application.

Serial dilutions of the filter-sterilised ADCs were made at a 1:10 ratio and repeated to produce eight serial dilutions, using a starting ADC concentration of 20 μg/ml and diluting in cell specific growth medium in sterile 96-well polypropylene plates. ADC dilutions (including the stock solution) were dispensed into 2 replicate wells, 100 μl/well, of the labelled white 96-well flat bottom plate, containing 100 μl seeded cell suspension. For media control wells 100 μl of cell growth medium was dispensed into 2 replicate wells, and for cell line control wells 100 μl of growth medium was dispensed onto 100 μl cell suspension, previously dispensed, into 2 replicate wells. All plates were incubated for 5 days in a 37° C. CO₂-gassed (5%) incubator. The assays were carried out using the same cell seeding densities and incubation times for both cell lines; 1×10³ cells/well incubated for 5 days each (these conditions have been previously optimised for this study).

After the 5 days incubation period, plates were centrifuged at 600 G (20° C.) for 5 mins, before 100 μl/well was carefully transferred onto the freshly prepared white 96-well flat bottom plates, containing 100 μl seeded Karpas-299 cells (previously dispensed). All plates were incubated for 5 days in a 37° C. CO₂-gassed (5%) incubator. After the incubation period, plates were centrifuged at 600 G (20° C.) for 5 mins, before 100 μl/well was carefully removed and discarded, and the cell viability was measured on the remaining medium in the wells using the CellTiter-Glo® assay. Plates were read on the Envision using the Luminescence protocol and data were analysed using Graphpad Prism software.

In vitro cytotoxicity in Karpas299 cells [nM] ConjA ConjB Primary culture 2.94 2.53 Media-transfer 0.016 3.77

SEQUENCES  [1H12 VH, CDR underline] SEQ ID NO. 1 QVQLVESGGGVVQPGRSLRLSCAASGFTFSSYGMSVVVRQAPGKGLEVVV ATISSGGSYTYYPDSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCAR HPIYYTYDDTMDYWGQGTTVTVSS [1H12 VL, CDR underline] SEQ ID NO. 2 EIVLTQSPGTLSLSPGERATLSCSASSSVSSGNFHWYQQKPGLAPRLLIY RTSNLASGIPARFSGSGSGTDFTLTISSLEPEDFAVYYCQQWSGYPWTFG GGTKLEIK [1H12 Heavy Chain] SEQ ID NO. 3 QVQLVESGGGVVQPGRSLRLSCAASGFTFSSYGMSVVVRQAPGKGLEVVV ATISSGGSYTYYPDSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCAR HPIYYTYDDTMDYWGQGTTVTVSSASTKGPSVFPLAPSSKSTSGGTAALG CLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSL GTQTYICNVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLF PPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPRE EQYN*STYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQ PREPQVYTLPPSREEMTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYK TTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLS LSPGK N* indicates Asn297  [1H12 Light Chain] SEQ ID NO. 4 EIVLTQSPGTLSLSPGERATLSCSASSSVSSGNFHWYQQKPGLAPRLLIY RTSNLASGIPARFSGSGSGTDFTLTISSLEPEDFAVYYCQQWSGYPWTFG GGTKLEIKRTVAAPSVFIFPPSDEQLKSGTASVVCLLNNFYPREAKVQWK VDNALQSGNSQESVTEQDSKDSTYSLSSTLTLSKADYEKHKVYACEVTHQ GLSSPVTKSFNRGEC [1H12 VH CDR1] SEQ ID NO. 5 SYGMS  [1H12 VH CDR2] SEQ ID NO. 6 TISSGGSYTYYPDSVKG  [1H12 VH CDR3] SEQ ID NO. 7 HPIYYTYDDTMDY  [1H12 VL CDR1] SEQ ID NO. 8 SASSSVSSGNFH  [1H12 VL CDR2] SEQ ID NO. 9 RTSNLAS  [1H12 VL CDR3] SEQ ID NO. 10 QQWSGYPWT  [murine 5F11 VH, CDR underline] SEQ ID NO. 11 EVKLLESGGGLVQPGGSLKLSCAASGFDFSRYWMSVVVRQAPGKGLEWIG EINPDSSTINYTPSLKDKFIISRDNAKNTLYLQMSKVRSEDTALYYCASP YYYGPFAYWGQGTLVTVSS [murine 5F11 VL, CDR underline] SEQ ID NO. 12 DIVLTQSPASLAVSLGQRAIISCKASQSVSFAGTSLMHWYQQKPGQQPKL LIYRASNLEAGFPTRFSGSGSRTDFTLNIHPVEEEDAATYYCQQSREYPR TFGGGTKLEVK [5F11 VH CDR1] SEQ ID NO. 13 RYWMS  [5F11 VH CDR2] SEQ ID NO. 14 EINPDSSTINYTPSLKD  [5F11 VH CDR3] SEQ ID NO. 15 PYYYGPFAY  [5F11 VL CDR1] SEQ ID NO. 16 KASQSVSFAGTSLMH  [5F11 VL CDR2] SEQ ID NO. 17 RASNLEA  [5F11 VL CDR3] SEQ ID NO. 18 QQSREYPRT  [5F11 RHA] SEQ ID NO. 19 QVQLVESGGGVVQPGRSLRLSCAASGFTFSRYWMSWVRQAPGKGLEVVVA EINPDSSTINYTPSLKDRFAISRDNSKNTLYLQMNSLRAEDTAVYYCASP YYYGPFAYWGQGTLVTVS [5F11 RHB] SEQ ID NO. 20 EVQLVESGGGLVQPGGSLRLSCAASGFTFSRYWMSWVRQAPGKGLEVVVA EINPDSSTINYTPSLKDRFTISRDNAKNSLYLQMNSLRAEDTAVYYCASP YYYGPFAYWGQGTLVTVS [5F11 RHC] SEQ ID NO. 21 EVQLLESGGGLVQPGGSLRLSCAASGFTFSRYWMSWVRQAPGKGLEVVVS EINPDSSTINYTPSLKDRFTISRDNSKNTLYLQMNSLRAEDTAVYYCASP YYYGPFAYWGQGTLVTVS [5F11 RKA] SEQ ID NO. 22 EIVLTQSPLSLPVTPGEPASISCKASQSVSFAGTSLMHWYLQKPGQSPQL LIYRASNLEAGVPDRFSGSGSGTDFTLKISRVEAEDVGVYYCQQSREYPR TFGQGTKVEIK [Human Axl] SEQ ID NO. 23 MAWRCPRMGRVPLAWCLALCGWACMAPRGTQAEESPFVGNPGNITGARGL TGTLRCQLQVQGEPPEVHWLRDGQILELADSTQTQVPLGEDEQDDWIVVS QLRITSLQLSDTGQYQCLVFLGHQTFVSQPGYVGLEGLPYFLEEPEDRTV AANTPFNLSCQAQGPPEPVDLLWLQDAVPLATAPGHGPQRSLHVPGLNKT SSFSCEAHNAKGVTTSRTATITVLPQQPRNLHLVSRQPTELEVAWTPGLS GIYPLTHCTLQAVLSDDGMGIQAGEPDPPEEPLTSQASVPPHQLRLGSLH PHTPYHIRVACTSSQGPSSWTHWLPVETPEGVPLGPPENISATRNGSQAF VHWQEPRAPLQGTLLGYRLAYQGQDTPEVLMDIGLRQEVTLELQGDGSVS NLTVCVAAYTAAGDGPWSLPVPLEAWRPGQAQPVHQLVKEPSTPAFSWPW VVYVLLGAVVAAACVLILALFLVHRRKKETRYGEVFEPTVERGELVVRYR VRKSYSRRTTEATLNSLGISEELKEKLRDVMVDRHKVALGKTLGEGEFGA VMEGQLNQDDSILKVAVKTMKIAICTRSELEDFLSEAVCMKEFDHPNVMR LIGVCFQGSERESFPAPVVILPFMKHGDLHSFLLYSRLGDQPVYLPTQML VKFMADIASGMEYLSTKRFIHRDLAARNCMLNENMSVCVADFGLSKKIYN GDYYRQGRIAKMPVKW1AIESLADRVYTSKSDVWSFGVTMWEIATRGQTP YPGVENSEIYDYLRRGNRLKQPADCLDGLYALMSRCWELNPQDRPSFTEL REDLENTLKALPPAQEPDEILYVNMDEGGGYPEPPGAAGGADPPTQPDPK DSCSCLTAAEVHPAGRYVLCPSTTPSPAQPADRGSPAAPGQEDGA [1H12 Heavy Chain] SEQ ID NO. 24 QVQLVESGGGVVQPGRSLRLSCAASGFTFSSYGMSVVVRQAPGKGLEVVV ATISSGGSYTYYPDSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCAR HPIYYTYDDTMDYWGQGTTVTVSSASTKGPSVFPLAPSSKSTSGGTAALG CLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSL GTQTYICNVNHKPSNTKVDKKVEPKSCDKTHTCPPCPAPELLGGPSVFLF PPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPRE EQYN*STYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQ PREPQVYTLPPSREEMTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYK TTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMHEALHNHYTQKSLS LSPG N* indicates Asn297  

1.-78. (canceled)
 79. A conjugate of formula (I): Ab-(DL)_(p)  (I) wherein: Ab is an antibody that binds to AXL; DL is

wherein: X is selected from the group comprising: a single bond, —CH₂— and —C₂H₄—; n is from 1 to 8; m is 0 or 1; R⁷ is either methyl or phenyl; when there is a double bond between C2 and C3, R² is selected the group consisting of: (ia) C₅₋₁₀ aryl group, optionally substituted by one or more substituents selected from the group comprising: halo, nitro, cyano, ether, carboxy, ester, C₁₋₇ alkyl, C₃₋₇ heterocyclyl and bis-oxy-C₁₋₃ alkylene; (ib) C₁₋₅ saturated aliphatic alkyl; (ic) C₃₋₆ saturated cycloalkyl; (id)

wherein each of R²¹, R²² and R²³ are independently selected from H, C₁₋₃ saturated alkyl, C₂₋₃ alkenyl, C₂₋₃ alkynyl and cyclopropyl, where the total number of carbon atoms in the R² group is no more than 5; (ie)

wherein one of R^(25a) and R^(25b) is H and the other is selected from: phenyl, which phenyl is optionally substituted by a group selected from halo, methyl, methoxy; pyridyl; and thiophenyl; and (if)

where R²⁴ is selected from: H; C₁₋₃ saturated alkyl; C₂₋₃ alkenyl; C₂₋₃ alkynyl; cyclopropyl; phenyl, which phenyl is optionally substituted by a group selected from halo, methyl, methoxy; pyridyl; and thiophenyl; when there is a single bond between C2 and C3, R² is

where R^(26a) and R^(26b) are independently selected from H, F, C₁₋₄ saturated alkyl, C₂₋₃ alkenyl, which alkyl and alkenyl groups are optionally substituted by a group selected from C₁₋₄ alkyl amido and C₁₋₄ alkyl ester; or, when one of R^(26a) and R^(26b) is H, the other is selected from nitrile and a C₁₋₄ alkyl ester; when there is a double bond between C2′ and C3′, R¹² is selected the group consisting of: (iia) C₅₋₁₀ aryl group, optionally substituted by one or more substituents selected from the group comprising: halo, nitro, cyano, ether, carboxy, ester, C₁₋₇ alkyl, C₃₋₇ heterocyclyl and bis-oxy-C₁₋₃ alkylene; (iib) C₁₋₅ saturated aliphatic alkyl; (iic) C₃₋₆ saturated cycloalkyl; (iid)

wherein each of R³¹, R³² and R³³ are independently selected from H, C₁₋₃ saturated alkyl, C₂₋₃ alkenyl, C₂₋₃ alkynyl and cyclopropyl, where the total number of carbon atoms in the R¹² group is no more than 5; (iie)

wherein one of R^(35a) and R^(35b) is H and the other is selected from: phenyl, which phenyl is optionally substituted by a group selected from halo, methyl, methoxy; pyridyl; and thiophenyl; and (iif)

where R²⁴ is selected from: H; C₁₋₃ saturated alkyl; C₂₋₃ alkenyl; C₂₋₃ alkynyl; cyclopropyl; phenyl, which phenyl is optionally substituted by a group selected from halo, methyl, methoxy; pyridyl; and thiophenyl; when there is a single bond between C2′ and C3′, R¹² is

where R^(36a) and R^(36b) are independently selected from H, F, C₁₋₄ saturated alkyl, C₂₋₃ alkenyl, which alkyl and alkenyl groups are optionally substituted by a group selected from C₁₋₄ alkyl amido and C₁₋₄ alkyl ester; or, when one of R^(36a) and R^(36b) is H, the other is selected from nitrile and a C₁₋₄ alkyl ester; and p is from 1 to
 8. 80. The conjugate according to claim 79, wherein X is —CH₂—.
 81. The conjugate according to claim 79, wherein n is 1 to
 4. 82. The conjugate according to claim 81, wherein n is
 2. 83. The conjugate according to claim 79, wherein there is a double bond between C2 and C3, and R² is a C₁₋₅ saturated aliphatic alkyl group.
 84. The conjugate according to claim 83, wherein R² is methyl, ethyl or propyl.
 85. The conjugate according to claim 79, wherein there is a double bond between C2 and C3, and R² is: (a) phenyl, which bears one to three substituent groups, wherein the substituents may be selected from methoxy, ethoxy, fluoro, chloro, cyano, bis-oxy-methylene, methyl-piperazinyl, morpholino and methyl-thiophenyl; or (b) cyclopropyl; or (c) a group of formula:

wherein the total number of carbon atoms in the R² group is no more than 3; or (d) the group:

or (e) a group of formula:

wherein R²⁴ is selected from H and methyl.
 86. The conjugate according to claim 79, wherein there is a single bond between C2 and C3, R² is

and (a) R^(26a) and R^(26b) are both H; (b) R^(26a) and R^(26b) are both methyl; or (c) one of R^(26a) and R^(26b) is H, and the other is selected from C₁₋₄ saturated alkyl, C₂₋₃ alkenyl, which alkyl and alkenyl groups are optionally substituted.
 87. The conjugate according to claim 79, wherein there is a double bond between C2′ and C3′, and R¹² is a C₁₋₅ saturated aliphatic alkyl group.
 88. The conjugate according to claim 87, wherein R¹² is methyl, ethyl or propyl.
 89. The conjugate according to claim 79, wherein there is a double bond between C2′ and C3′, and R¹² is: (a) phenyl, which bears one to three substituent groups, wherein the substituents may be selected from methoxy, ethoxy, fluoro, chloro, cyano, bis-oxy-methylene, methyl-piperazinyl, morpholino and methyl-thiophenyl; or (b) cyclopropyl; or (c) a group of formula:

wherein the total number of carbon atoms in the R¹² group is no more than 3; or (d) the group:

or (e) a group of formula:

wherein R³⁴ is selected from H and methyl.
 90. The conjugate according to claim 79, wherein there is a single bond between C2′ and C3′, R¹² is

and (a) R^(36a) and R^(36b) are both H; or (b) R³⁶ and R^(36b) are both methyl; or (c) one of R^(36a) and R^(36b) is H, and the other is selected from C₁₋₄ saturated alkyl, C₂₋₃ alkenyl, which alkyl and alkenyl groups are optionally substituted.
 91. The conjugate according to claim 79, wherein the antibody comprises a VH domain comprising a VH CDR3 with the amino acid sequence of SEQ ID NO.7, a VH CDR2 with the amino acid sequence of SEQ ID NO.6, and a VH CDR1 with the amino acid sequence of SEQ ID NO.5.
 92. The conjugate according to claim 79, wherein the antibody comprises a VH domain having the sequence of SEQ ID NO.1.
 93. The conjugate according to claim 79, wherein the antibody comprises a VL domain comprising a VL CDR3 with the amino acid sequence of SEQ ID NO.10, a VL CDR2 with the amino acid sequence of SEQ ID NO.9, and a VL CDR1 with the amino acid sequence of SEQ ID NO.8.
 94. The conjugate according to claim 79, wherein the antibody comprises a VH domain having the sequence of SEQ ID NO.
 2. 95. The conjugate according to claim 79, wherein the antibody comprises a heavy chain having the sequence of SEQ ID NO. 3 or SEQ ID NO.
 24. 96. The conjugate according to claim 79, wherein the antibody comprises a paired with a light chain having the sequence of SEQ ID NO.
 4. 97. A composition comprising a mixture of the antibody-drug conjugate compounds as defined in claim 79, wherein the average drug loading per antibody in the mixture of antibody-drug conjugate compounds is about 1 to about
 4. 98. A pharmaceutical composition comprising the conjugate of claim 79, and a pharmaceutically acceptable diluent, carrier, or excipient.
 99. The pharmaceutical composition of claim 95, further comprising a therapeutically effective amount of a chemotherapeutic agent.
 100. A method of treating cancer comprising administering to a patient the pharmaceutical composition of claim
 98. 101. The method of claim 100, wherein the patient is administered a chemotherapeutic agent in combination with the conjugate. 